STUDIES OF THE ANNUAL CYCLE OF THE SWALLOW-TAILED

KITE (ELANOIDES FORFICATUS): MIGRATION, HABITAT USE,

AND PARASITES

A Thesis

Presented to

the College of Graduate Studies of

Georgia Southern University

_____________________________

In Partial Fulfillment

of the Requirements for the Degree

Master of Science

In the Department of Biology

_____________________________

by

Gina Marie Zimmerman

May 2004

ACKNOWLEDGMENTS

I would like to thank the following for their various contributions to the project. Dr. C.

Ray Chandler provided guidance as an advisor and mentor, and genuine friendship. Dr. Kenneth

Meyer provided inspiration and support to make this research possible. My committee members,

Drs. Lissa Leege and Steve Vives gave advice and encouragement throughout my enrollment at

GSU. Drs. Susan Langley and Nancy Leathers offered many hours of technical assistance with

GIS. Drs. Lance Durden and Oscar Pung of GSU and Dr. Heather Proctor at the University of

Alberta, Canada, assisted in preparation and identification of parasites.

I thank Emily Jo Williams and the Georgia Department of Natural Resources for the use

of satellite-tracking data, VHF–radio frequencies, and nest locations; Jennifer Coulson of Tulane

University, John Cely of the South Carolina Department of Natural Resources, and Jim Elliott of

the South Carolina Center for Birds of Prey for the use of their VHF radio-tagged kites; Paul

Howey and the staff of Microwave Telemetry, Inc.; Brad Mueller of American Wildlife

Enterprises, Inc; and Andy Day, Jamie Duberstein, Jeff Kingscott, Kristine Lightner, Bill Marrs,

Bradley Richardson, Stacie Schoppman, Diana Swan, and Audrey Washburn for field assistance.

For the international work, I thank Marco Lazcano, Gonzalo Merediz, and Barbara

MacKinnon of Amigos de Sian Ka’an; Edilberto Romero, Wilber Sanchez, and Gina Young of

Programme for Belize; Valdemar Andrade and Roberto Pott of Belize Audubon Society; Omar

Figueroa of Aves Sin Fronteras and Len Zeoli of the Peace Corps. I also thank Alberto Saab, the

pilots of AeroSaab, Taxi Aereo and Jorge Coughanour (flying in Mexico) and Frank Plett (flying

in Belize).

iii

This research was funded primarily by the Florida Fish and Wildlife Conservation

Commission and Disney’s Wildlife Conservation Fund. Other funding was generously provided

from the Cooper Ornithological Society’s Mewalt-King Research Grant, the Association of Field

Ornithologists’ E. Alexander Bergstrom Memorial Research Fund, the Georgia Ornithological

Society’s H. Branch Howe, Jr., Research Grant, the Greater Piedmont Region branch of the

Explorer’s Club, and Georgia Southern University's Competitive Research Grant and Academic

Excellence Award.

iv

ABSTRACT

STUDIES OF THE ANNUAL CYCLE OF THE SWALLOW-TAILED KITE (ELANOIDES

FORFICATUS): MIGRATION, HABITAT USE, AND PARASITES

May 2004

GINA MARIE ZIMMERMAN

B.S. UNIVERSITY OF WISCONSIN-STEVENS POINT

M.S. GEORGIA SOUTHERN UNIVERSITY

Directed by: Professor C. Ray Chandler

The Swallow-tailed Kite (Elanoides forficatus) is a rare Neotropical migrant raptor that

breeds in the United States and winters in South America. Despite intense conservation concern,

relatively little is known about the factors that may limit Swallow-tailed Kite populations. I

examined three aspects of the annual cycle that could have conservation significance: stopover

behavior on Cuba and the Yucatan Peninsula, range-wide habitat associations, and parasites.

Because Cuba and the Yucatan Peninsula are situated along the migratory route after a long over-

water crossing, they may be potentially important stopover sites. To examine this prediction, 29

satellite-tracked kites from the U.S. were monitored to quantify migration rates and movements.

Swallow-tailed Kites do not show significant stopover on Cuba. However, as predicted, kites

slowed down and moved around the Yucatan more than any other location along the migration

route. Locations from satellite-tracked and VHF-tagged birds were also analyzed to determine

habitat use versus availability in the Yucatan using GIS. Kites selected low forests and avoided

disturbed areas and areas without vegetation. I examined habitats use on a range-wide scale to

see if kites were more selective during one season than others. Nests and satellite-telemetry

v

locations were analyzed with GIS to assess broad-scale habitat associations during the breeding,

stopover, and winter phases of the annual cycle. I found that kites were associated with forest

habitats in all seasons. However they use forests more than expected by chance during winter

and breeding, and less than expected during stopover. Additionally, kites only preferred wetlands

during the breeding season. Kites were most selective (use differed from availability by the

greatest amount) in habitat choice during the breeding season. Lastly, kites in Florida and

Georgia were examined for blood parasites (blood smears) and ectoparasites (dusted with

pyrethrin). I found one trypanosome and two microfilaria in the blood of three birds. This was

the first time kite blood had been examined for parasites. I found six ectoparasite species (mean

of 21.5 specimens/individual), including three Mallophagan chewing lice (Cuculiphilus

decoratus, Colpocephalum osborni, and Degeeriella guimaraesi), one blood sucking mite

(Ornithonyssus bursa), and two undescribed mites (Acari: Gabuciniidae). The new mites include

an Aetacarus sp. and a species that may represent a new genus. My results expand our

knowledge of the annual cycle of the Swallow-tailed Kite, thereby improving opportunities of

conservation for this rare species.

vi

TABLE OF CONTENTS

Page

ACKNOWLEDGMENTS..................................................................................................................iii

ABSTRACT........................................................................................................................................ v

LIST OF TABLES ............................................................................................................................. ix

LIST OF FIGURES...........................................................................................................................xii

Chapter I Introduction ......................................................................................................................... 1

Chapter II The Importance of Cuba and the Yucatan Peninsula as Stopover Sites for Migrating Swallow-tailed Kites .......................................................................................................................... 4

Introduction...................................................................................................................................... 4

Methods ........................................................................................................................................... 9

Results ........................................................................................................................................... 25

Discussion...................................................................................................................................... 49

Chapter III Habitat Associations of Swallow-tailed Kites During Three Phases of Their Annual Cycle ................................................................................................................................................ 58

Introduction.................................................................................................................................... 58

Methods ......................................................................................................................................... 60

Results ........................................................................................................................................... 70

Discussion...................................................................................................................................... 84

Chapter IV The Blood Parasites and Ectoparasites of Swallow-tailed Kites in Florida and Georgia ........................................................................................................................................................... 92

Introduction.................................................................................................................................... 92

Methods ......................................................................................................................................... 94

Results ........................................................................................................................................... 98

Discussion...................................................................................................................................... 99

vii

TABLE OF CONTENTS (Continued)

Chapter V Summary ....................................................................................................................... 107

LITERATURE CITED ................................................................................................................... 111

APPENDICES................................................................................................................................. 122

Appendix A. The following pages (124-129) show the individual southbound migration routes of 25 Swallow-tailed Kites tracked by satellite from the western shore of Cuba through the Yucatan Peninsula that migrated in years 2000 to 2003................................................................................ 123

Appendix B. Southbound migration of Swallow-tailed Kite #16083 tracked by satellites in 2002 and 2003. ......................................................................................................................................... 130

Appendix C. The southbound migration of Swallow-tailed Kite #16031 from Florida through Nicaragua tracked by satellites in 2002........................................................................................... 131

viii

LIST OF TABLES

Table Page 2.1. Summary of adult Swallow-tailed Kites tracked by satellite (1996-2003) that were used

for analysis of migration rates and habitat use. ...................................................................... 12 2.2. Length and descriptions of 12 migration sections used for the analysis of Swallow-tailed

Kite migration. These sections define the Swallow-tailed Kites’ migratory pathway from the southern tip of Florida through the southern-most winter regions in South America ............ 16

2.3. Ten GIS habitat classes available for Mexico and the six habitat classes used in the

habitat analysis. ...................................................................................................................... 22 2.4. Twelve GIS habitat classes available for Belize and the six habitat classes used in the

habitat analysis. ...................................................................................................................... 24 2.5. Fifteen locations of ten individual VHF radio-tagged Swallow-tailed Kites detected in

Mexico and Belize, 2002 and 2003. ....................................................................................... 26 2.6. Migration arrival timetable for Swallow-tailed Kites migrating from Florida to their

winter range, 2002, 2003, and 2000-2003 combined. Section # correspond with Table 2.2.. 28 2.7. Sample sizes of Swallow-tailed Kites used in migration analyses of four migration

variables in 12 migration sections in 2002, 2003 and 2000-2003 combined.......................... 32 2.8. Comparison of habitat use within 1,500 m of all satellite-tracked Swallow-tailed Kite

locations to available habitat and to random locations in Quintana Roo, Mexico, and the comparison of the mean habitat use of individual kites to available habitat. ......................... 36

2.9. Components of variation in habitat use and diversity index by individual migrant

Swallow-tailed Kites that had more than 1 location in Quintana Roo Mexico (n = 13) and Peninsular Mexico (n = 16). ................................................................................................... 38

2.10. Comparison of the sex differences in habitat use and diversity index within 1,500 m of

radio-tagged Swallow-tailed Kite locations in Quintana Roo and Peninsular Mexico........... 39 2.11. Principal component analysis of habitat within random locations (n = 59) in Quintana

Roo, Mexico. .......................................................................................................................... 40 2.12. Comparison of principal component scores from sites used by Swallow-tailed Kites to

those of random locations (n = 59) in Quintana Roo, Mexico. .............................................. 41

ix

LIST OF TABLES (Continued) Page 2.13. Comparison of the proportions of habitats available to those within 1,500 m of

locations of all migrating Swallow-tailed Kite locations and the mean proportions of individuals in Belize. .............................................................................................................. 42

2.14. Comparison of the proportions of habitats and the diversity index within 1,500 m of

migrating radio-tagged Swallow-tailed Kites (n = 34) to those of random locations in Belize................................................................................................................................................. 43

2.15. Comparison of males (n = 13) to females (n = 19) in habitat use and diversity index

within 1,500 m of radio-tagged Swallow-tailed Kite locations in Belize............................... 45 2.16. Components of variation in habitat use by individual migrant Swallow-tailed Kites that

had more than 1 location throughout Belize........................................................................... 46

2.17. Pricipal components analysis of habitat within random points (n = 34) in B elize…...47 2.18. Comparison of principal component scores from sites used by Swallow-tailed Kites to those of random locations (n = 34) in Belize. ......................................................................... 48 3.1. Eighteen GLC2000 land covers found within Swallow-tailed Kite breeding, stopover,

and winter ranges and their combination into six basic habitat classifications that were directly comparable among regions........................................................................................ 69

3.2. Comparison of habitat use (within 5 km of nest and satellite locations) of Swallow-tailed

Kites to the proportions of the available broad-scale habitats within the breeding, stopover, and wintering area. ................................................................................................................. 72

3.3. Comparison of the proportion of the GLC2000 habitat classifications within 5 km of nest

locations of Swallow-tailed Kites (n = 477) to the proportions of available habitats within the breeding area........................................................................................................................... 74

3.4. Comparison of the proportion of the GLC2000 habitat classifications within 5 km of

satellite-tracked Swallow-tailed Kite locations (n = 114) to the proportions of available habitats within the stopover area. ........................................................................................... 75

3.5. Comparison of the proportion of the broad habitat classifications within 5km of satellite-

tracked Swallow-tailed Kite locations (after combining individual locations, n = 25) to the proportions of available habitats within stopover on the Yucatan Peninsula. ........................ 76

3.6. Components of variation in habitat use by individual migrant Swallow-tailed Kites that

had more than 1 location in the stopover area (n = 25) and winter area (n = 14)................... 77

x

LIST OF TABLES (Continued) Page 3.7. Comparison of the proportion of the GLC2000 habitat classifications within 5 km of

satellite-tracked Swallow-tailed Kite locations (n = 440) to the proportions of available habitats within the winter area in South America................................................................... 78

3.8. Comparison of the proportion of the broad habitat classifications within 5 km of

satellite-tracked Swallow-tailed Kite locations (after combining individual locations, n = 14) to the proportions of available habitats within the winter area in South America.................. 80

3.9. Principal component analysis of habitats at sites used by Swallow-tailed Kite (nest and

satellite locations n = 1031) throughout breeding, stopover and wintering seasons. ............. 81 4.1. Trapping location, age, and sex of 38 Swallow-tailed Kites sampled for blood parasites

and ectoparasites in 2002 and 2003. ....................................................................................... 96 4.2. Prevalence and intensity of ectoparasites from 37 adult and nestling Swallow-tailed

Kites examined in Florida and Georgia in 2002 and 2003. .................................................. 100 4.3. Comparison of ectoparasite intensity/bird performed on five species of ectoparasites and

total ectoparasite loads of 37 Swallow-tailed Kites sampled in 2002 and 2003. P values based on Mann-Whitney U-tests. ................................................................................................... 101

xi

LIST OF FIGURES

Figure Page 2.1. Migration route of the Swallow-tailed Kite from breeding sites in Florida and Georgia

to wintering sites in South America as indicated by locations of satellite-tracked kites (n = 29 migrations), 2000 to 2003......................................................................................................... 6

2.2. The 12 migratory sections partitioned along the Swallow-tailed Kite’s migratory route

used in the migration rate analysis.......................................................................................... 15 2.3. Example of the distances used in the calculation of the four movement variables used to

estimate stopover of Swallow-tailed Kites ............................................................................. 18 2.4. Mean (± SE) movement rate (km/hr) within 12 geographic regions for southbound

Swallow-tailed Kite migrants across 3 year-categories. See Table 2.7 for section descriptions............................................................................................................................. 29

2.5. Mean (± SE) progress rate (km/hr) within 12 geographic regions for southbound

Swallow-tailed Kite migrants across 3 year-categories. See Table 2.7 for section descriptions................................................................................................................................................. 30

2.6. Mean (± SE) net migration rate (km/hr) within 12 geographic regions for southbound

Swallow-tailed Kite migrants across 3 year-categories. See Table 2.7 for section descriptions............................................................................................................................. 31

2.7. Southbound migration of Swallow-tailed Kites tracked by satellite from Florida through

the Yucatan Peninsula in 2002 and 2003 (n = 23 migrations)................................................ 33 2.8. Mean (± SE) stopover index of migration within 12 geographic regions for southbound

Swallow-tailed Kite migrants across 3 year-categories. See Table 2.7 for section descriptions............................................................................................................................. 35

3.1. Swallow-tailed Kite nest locations (n = 477) and the area defined as available for the

breeding season in the hemisphere-wide habitat analysis. ..................................................... 61 3.2. Swallow-tailed Kite telemetry locations (n = 114, from 29 individuals) and the area

defined as available for stopover used in the hemisphere-wide habitat analysis.................... 62 3.3. Swallow-tailed Kite telemetry locations (n = 440 from 14 individuals) and the area

defined as available for the winter season in the hemisphere-wide habitat analysis. ............. 63

xii

LIST OF FIGURES (Continued) Page 3.4. Interrupted Goode’s Homolosine projection (Goode 1925), a "lobed" equal-area

projection that displays areas linearly proportional to the corresponding region on the sphere, used in the Global Land Coverage (GLC2000) for the hemisphere-wide habitat analysis. ... 67

3.5. The distribution of the available proportion of the broad scale habitats used by Swallow-

tailed Kites throughout their annual cycle (breeding, stopover, winter)................................. 71 3.6. Swallow-tailed Kite habitat use (open circles) in comparison to the available habitat

(closed circles) in three regions throughout the annual cycle (Red, breeding; green, stopover; blue, winter). Points are mean principal component scores. .................................................. 82

3.7. The pattern of forest habitat use (PC1) of Swallow-tailed Kites for breeding, stopover,

and winter seasons as determined by a principal components analysis.................................. 83 3.8. The pattern of wetland habitat use (PC2) of Swallow-tailed Kites for breeding, stopover,

and winter seasons as determined by a principal components analysis.................................. 85 4.1. Collection locations in Georgia and Florida for blood parasites and ectoparasites from

Swallow-tailed Kites in 2002 and 2003.................................................................................. 95

xiii

Chapter I

Introduction

The northern subspecies of the Swallow-tailed Kite (Elanoides forficatus forficatus) is a

Neotropical migrant that breeds in the southeastern United States and winters in the central South

American countries of Brazil, Paraguay, and Bolivia. Swallow-tailed Kites inhabit the

southeastern United States from early March to early August, while spending the rest of the year

along their 8000-km migration route and wintering grounds (Meyer and Collopy 1995).

The Swallow-tailed Kite is an agile and conspicuous raptor with a deeply forked tail and

contrasting black and white wings on a white body. Exceedingly efficient in flight, the Swallow-

tailed Kite spends most of its day in the air catching and eating prey as it flies (Meyer et al. 2004).

While insects are the mainstay of the adults’ diet (Millsap 1987, Meyer 1998), kites will also

glean frogs, lizards, snakes, and nestling birds from the forest canopy to feed their young (Meyer

1995, Gerhardt et al. 2004, Meyer et al. 2004). Swallow-tailed Kites prefer nest sites within a

wetland forest with an uneven canopy (Meyer 1995). These sites are found within heterogeneous

landscapes (areas with patches of different habitats such as forests, fields, and marsh) that provide

foraging opportunities. The nest of small sticks and epiphytes (e.g., Spanish moss, Tillandsia

usneoides) is usually found near the top of one of the tallest trees in the stand (often Pinus spp.)

(Meyer 1995). The height of the nest allows the kites to enter and exit without the interference of

other trees.

From 1880 to 1940, the Swallow-tailed Kite declined from being a common breeder in as

many as 21 states to uncommon or rare in its present distribution in parts of only seven

southeastern states (Cely 1979, Meyer 1995). Suggested causes include the loss of nesting habitat

2

in bottomland forests as the country was settled in the 1900s. Additionally, the kite’s decline can

be attributed to the loss of natural foraging habitats such as prairies and wetlands and to being

hunted (Cely 1979) on their breeding grounds as well as on migration and winter grounds. Meyer

(1995) has estimated that there may be as few as 3,200-4,600 individuals in the United States.

Because of this precipitous decline, a nationally recognized bird conservation

organization, Partners in Flight, ranks the Swallow-tailed Kite as a top priority species for

conservation action in the U.S. (Partners in Flight 2003). A status assessment based on the

conservative guidelines of the International Union for the Conservation of Nature (IUCN)

concluded that the Swallow-tailed Kite qualifies for the U.S. federal status of Threatened (D.

Swan and K. Meyer, pers. comm.), and the species has also been recommended for consideration

as federally endangered (Meyer and Collopy 1996).

Despite this high conservation priority, little is known about the basic ecology and

demography of Swallow-tailed Kites. There is a pressing need for research that addresses the

biology of this species as well as the factors that may be contributing to its rarity. Therefore, the

overall goal of my research is to provide data on the basic ecology of this poorly known raptor.

In particular, my study focuses on three issues during the annual cycle that may have appreciable

conservation significance. In Chapter II, I test the prediction that Cuba or eastern Mexico and

Belize (hereafter, referred to collectively as the Yucatan Peninsula) are used as stopover sites

during southbound migration. In Chapter III, I examine habitat associations during breeding,

stopover and wintering seasons to determine whether habitat selectivity (and possibly habitat

limitation) is greater during some phases of the annual cycle than others. Finally, in Chapter IV, I

describe the abundance and diversity of blood parasites and ectoparasites from nestling and adult

Swallow-tailed Kites from study populations in Florida and Georgia.

3

My research provides insight into some of the potential challenges Swallow-tailed Kites

face throughout their annual cycle, including the need to find appropriate stopover sites, locate

suitable habitat over two continents, and avoid excessive infestation by parasites. The data

presented here provide preliminary information for management action on the conservation needs

for this rare raptor.

Chapter II

The Importance of Cuba and the Yucatan Peninsula as Stopover Sites for

Migrating Swallow-tailed Kites

Introduction

The Swallow-tailed Kite breeds in the southeastern United States and migrates in the fall

to wintering areas in South America. While hunting and habitat loss on the breeding grounds are

among the most likely causes of a breeding range contraction from 21 to 7 southeastern states

(Cely 1979, Robertson 1988, Meyer 1995), Swallow-tailed Kites face challenges throughout their

annual cycle. Unfortunately, many aspects of this annual cycle are poorly documented or

unknown. This is especially true of the Swallow-tailed Kite’s long migration to the Neotropics.

Migration is a strenuous event performed each year by millions of individual birds representing

many species (Keast and Morton 1980). Many of these migrants succumb to adverse weather,

energetic stress, and exposure to novel predators en route (Moore et al. 1990). In the case of the

Swallow-tailed Kite, events along the migration route may be key to understanding this species’

rarity.

However, only recently has the Swallow-tailed Kite’s route from breeding grounds to

winter ranges been defined. In 1996, the Avian Research and Conservation Institute (ARCI)

began deploying satellite transmitters on breeding kites in Florida, eventually describing the

narrow 8000-km migration corridor to wintering areas in Brazil, Paraguay, and Bolivia (K.

Meyer, unpubl. data). This new satellite-tracking technology has helped researchers discover the

migration routes of several other species of raptors as well (Fuller et al. 1998, Ueta et al. 2000,

Martell et al. 2001, Meyburg et al. 2003).

5

Satellite tracking uses polar-orbiting NOAA satellites that detect a unique signal from a

platform transmitter terminal (PTT) attached to each bird (Argos 1996). This technology

provides valuable remote location and movement data on a global scale over long time periods

(Ginati et al. 1995). Together with traditional banding data and stable isotope analysis (Marra et

al. 1998, Hobson et al. 2001), satellite telemetry is permitting scientists to link the breeding

populations of some species to their wintering grounds with a defined migratory route. However,

basic ecology and conservation needs along the migration route often remain understudied for

these species. This is certainly the case with the Swallow-tailed Kite.

Two-thirds of the North American breeding population of Swallow-tailed Kites nests in

Florida (Meyer 1995), while the other one-third is dispersed among seven other southeastern

coastal states. During migration, the majority of kites pass through peninsular Florida, cross the

200-km Straits of Florida to Cuba, then fly another 200 km to the Yucatan Peninsula of Mexico

and Belize. Other populations of kites from Georgia and South Carolina may join kites from

Alabama, Mississippi, Louisiana and Texas in migrating around the Gulf of Mexico (K. Meyer,

unpubl. data), reuniting with their conspecifics in Honduras. From here, all North American kites

continue along the eastern edge of Central America into Columbia where they cross the Andes

and head southeast to winter sites in southwestern Brazil, eastern Paraguay, and Bolivia (Fig.

2.1).

Many migrant birds repeatedly use certain locations and habitats as rest areas or

stopovers on the way to and from breeding and wintering sites (Moore et al. 1990, Pfister et al.

1998, De Leon and Smith 1999). A stopover site is a place where a migrant pauses for some

length of time (usually ≥ 24 hr for passerines) between migratory flights (Moore 2000). These

locations are vital for birds to replenish energy reserves (Berthold 1975, Blem 1980, Bairlein

6

Figure 2.1. Migration route of the Swallow-tailed Kite from breeding sites in Florida and Georgia to wintering sites in South America as indicated by locations of satellite-tracked kites (n = 29 migrations), 2000 to 2003.

7

1985, Biebach et al. 1986, and Moore and Kerlinger 1987) and water loss (Carmi et al. 1992), and

as resting places (Moore et al. 1993). Some birds use stopover sites to avoid flight during

inclement weather and to wait for favorable weather systems to facilitate a more efficient

migration (Safriel and Lavee 1988, Kerlinger 1989, Latta and Brown 1999).

Unlike songbirds, which use a relatively small area or patch of stopover habitat, the

highly mobile Swallow-tailed Kite can cover many square kilometers in a short period of time.

Their remarkably efficient flight permits them to stay aloft for hours, promoting a foraging

strategy of searching for flying insects and arboreal vertebrates in the forest canopy (Meyer et al.

2004). Because most of the literature on stopover pertains to songbirds, ducks, and shorebirds, it

is necessary, perhaps, to redefine stopover for birds that use the landscape on a different spatial

scale, such as raptors.

Stopover sites are especially important before and after birds cross dangerous ecological

barriers such as deserts (Biebach et al. 1986, Safriel and Lavee 1988) and large bodies of water

(Petit et al. 1992, Moore et al. 1993). At these times, birds become concentrated in isolated

patches of habitat that in turn could make them vulnerable to disturbance. Raptors may become

particularly vulnerable to environmental contaminants and hunting (Senner and Fuller 1989) at

these times. Because of an increased energy demand after long passages over geographical

barriers, resource competition is also magnified (Moore and Yong 1991).

There is some evidence that the over-water crossing to the Yucatan Peninsula may carry

significant costs for the Swallow-tailed Kite. Comparative radio-tracking studies of Swallow-

tailed Kites show that prior to migration, juvenile survival is equivalent between Florida and

Louisiana (K. Meyer and J. Coulson, unpubl. data). At one year old, however, at least twice as

many radio-tagged young have returned to Louisiana than to Florida after the spring migration.

The obvious speculation is that mortality of Florida young may be high because of the dangers

8

associated with crossing large expanses of water, whereas kites in Louisiana migrate around the

Gulf of Mexico (see Appendix C). Even though raptors’ avoidance of long water-crossings has

been well documented (Kerlinger 1989, and Meyer et al. 2000) the majority of kites choose this

riskier route. Flying across large bodies of water as opposed to following the coast is a tradeoff

between risk and total migration distance (Bruderer and Liechti 1998).

Swallow-tailed Kites must fly between 400 and 770 km over water en route from Florida

to the Yucatan. If kites bypass Cuba, the entire route−a minimum of 770 km−is over water.

Alternatively, kites might make a 200-km southwesterly crossing from Florida to Cuba, proceed

over land across western Cuba, and make another 200-km water crossing to the Yucatan.

Reaching the Yucatan Peninsula could well be the most serious challenge faced by the majority

of migrating Swallow-tailed Kites because upon landfall they need the proper resources for

resting and feeding. From there, the remaining journey to South America lies entirely over land.

There are two potentially important stopover sites associated with the water crossing

along the Swallow-tailed Kite’s route. The first is Cuba. Cuba might be a rest stop for kites as it

is for many other North American migrants (Gonzóles-Alonso et al. 1992). The second is the

Yucatan Peninsula, which is known as an important wintering area for many migratory songbirds

as well (Lynch 1989a, Greenberg 1992), in addition to supporting many endemic species (Stotz et

al. 1996).

Unfortunately, the highest rates of deforestation in Latin America are occurring in

Mexico as well as Central America, and the Caribbean Islands (Myers 1980, Buschbacher 1986),

which together comprises at least half of the Swallow-tailed Kites’ migratory route. In the states

of Quintana Roo and Campeche, Mexico, extensive old-growth forests have been encroached

upon by mechanized agriculture and large-scale cattle ranching (Lynch 1989b). Forest

degradation in stopover sites increases the cost of migration, perhaps jeopardizing bird survival

9

(Moore and Simons 1989). Identifying regions and habitats on Cuba or the Yucatan Peninsula

that Swallow-tailed Kites occupy and depend upon may provide a basis for protecting these areas

from further development and contribute to the conservation of a broader range of migratory birds

and other wildlife.

Satellite technology has only recently shown that Swallow-tailed Kites migrate through

Cuba and the Yucatan Peninsula, yet the degree to which they depend on these regions for rest

and food sources is unknown. Therefore, the objective of my study was to quantify these

stopover possibilities. I hypothesized that Cuba, eastern Mexico, and Belize serve as stopover

sites for migrating Swallow-tailed Kites. Specifically, I tested three predictions about the spatial

and temporal use of Cuba and the Yucatan. I predict that 1) the kites will have a slower migration

rates in Cuba and in the Yucatan than in adjacent areas, 2) kites will wander more widely in these

area than along other portions of the route (i.e., birds will wander as they search out appropriate

foraging and roosting sites), and 3) the kites will choose specific locations and certain habitat

features over others in the areas that show evidence of stopover.

Methods

Telemetry. − During the breeding season (May-July), adult (> 1 year of age) and nestling

Swallow-tailed Kites were captured and fitted with radio transmitters in four states: Florida

(Avian Research and Conservation Institute, ARCI), Georgia (ARCI), Louisiana (Jennifer

Coulson, Tulane University), and South Carolina (John Cely, South Carolina Department of

Natural Resources; Jim Elliott, South Carolina Center for Birds of Prey). These organizations

tagged Swallow-tailed Kites for various studies of demography, dispersal, home range, and

migration. Adult kites were lured into a large (12 m x 8 m, 9-cm mesh) mist-net (Avinet, Inc.)

using a live Great Horned Owl (Bubo virginianus) to elicit mobbing by kites in defense of their

young. Nestlings 28-33 days old were accessed by climbing the nest tree. A 1-cc blood sample

10

was collected from the brachial vein of each kite for DNA sex determination (Zoogen, Inc., Avian

Biotech International, Inc.).

Backpack harnesses of 6-mm−wide Teflon ribbon (Bally Ribbon Mills Inc.) were affixed

to adults and young supporting either an 11-g conventional VHF-radio transmitter or an 18-g

solar-powered PTT, which produced a signal that was read by orbiting satellites. The VHF-

transmitters had an expected life span of about 27 months (American Wildlife Enterprises Inc.)

and were relocated using a handheld Yagi three-element antenna or a roof-mounted dipole whip

antenna (Advanced Telemetry Systems Inc) from as far as 8 km on the ground or 100 km from a

single-engine airplane with two-element H-antennas (Telonics, Inc).

Satellite transmitters had a duty cycle of 10 hrs on followed by 22 hrs off to recharge

storage batteries and were expected to last at least 4-5 years, as long as they remained on the bird

and were exposed to sufficient sunlight to recharge (Microwave Telemetry, Inc). The signals

were processed into location reports by Service Argos, Inc. and delivered every other day via the

Internet. Each bird produced 0-5 locations per day, but only a fraction (0-2 on average) of these

had an accuracy level or Location Class (LC) adequate for my analysis. Although the most

accurate fixes (LC 3) only had a 67% probability of being within 150 m of the actual location

(Argos 1996), the value of satellite telemetry permits relatively continuous tracking from remote

locations (Ginati et al. 1995).

In 2002, 53 individual adult kites (13 from Florida, 4 in Georgia, 14 in South Carolina, 22

in Louisiana) and 38 nestlings (12 in Georgia, 12 in South Carolina, 14 in Louisiana) were fitted

with VHF transmitters. In 2003, 78 adults (6 from Florida, 20 in Georgia, 19 in South Carolina,

33 in Louisiana) and 23 nestlings (8 in Georgia, 12 in South Carolina, three in Louisiana) were

tracked, some of which were also tracked in 2002. Because some individuals carried a

11

transmitter in both years, the 192 VHF frequencies for which I searched represented a total of 116

individuals.

Satellite transmitters were placed only on adult kites breeding in Florida and Georgia

(Table 2.1). I also used ARCI’s past migration data from Florida-tagged birds from 1996 (four),

1998 (one), 2000 (two) and 2001 (four). In 2002, I monitored ten satellite-tracked birds from

Florida and an additional four tagged in Georgia. In 2003, I tracked nine kites from Florida and

four from Georgia. Many of the birds fitted with a solar-powered transmitter in one year still had

live transmitters (and were tracked again) in subsequent years (15 birds for one migration, 8 for

two migrations, and one for three migrations). Thus, I obtained satellite-tracking data for a total

of 34 Swallow-tailed Kite migrations representing 24 different individuals (18 from Florida and 6

from Georgia).

Fieldwork in the Yucatan Peninsula.− In 2002 and 2003, I conducted ground surveys in

eastern Mexico and Belize to locate Swallow-tailed Kites migrating from the United States. In

2002, fieldwork began in Quintana Roo, Mexico, on 24 July through 9 August, and ended in

Belize from 10 to 24 August. In 2003, I was in Mexico (Quintana Roo and Yucatan States) for

approximately one week (31 July to 8 August) and in Belize two weeks (9 to 21 August). Using a

programmable receiver, I scanned for frequencies of migrating VHF radio-tagged kites from the

U.S. study population from elevated terrain and along major highways and secondary roads

throughout Quintana Roo, Yucatan, and Belize. Additionally, I flew in a small plane along

bearings that provided the best coverage for detecting VHF-tagged kites throughout Quintana

Roo, northwestern Yucatan, and Belize. Tracking routes were planned to drive or fly by the

available satellite-derived locations on the assumption that the VHF-tagged kites used the same

areas.

12

Table 2.1. Summary of adult Swallow-tailed Kites tracked by satellite (1996-2003) that were used for analysis of migration rates and habitat use.

Bird ID Sex State

tagged County tagged

Years monitored

A-3 Female FL Collier 1996 M-24 Female FL Collier 1996 Steve's Female FL Highlands 1996 Steve's juv Female FL Highlands 1996 Beetle Male FL Levy 1998 OWP Female FL Orange 2001 Woodruff Female FL Volusia 2001 16081 Female GA Brantley 2002 16085 Female GA Camden 2002 36309 Female FL Levy 2002 36312 Female FL Levy 2002 36314 Male FL Levy 2002 36315 Male FL Levy 2002 41244 Male GA Camden 2003 36314b Male GA Glynn 2003 Tiger Creek Female FL Polk 2000, 2001 16082 Female FL Levy 2001 to 2003 16086 Male FL Levy 2001, 2002 16083 Male GA Camden 2002, 2003 36308 Female FL Levy 2002, 2003 36310 Male FL Levy 2002, 2003 36311 Male FL Levy 2002, 2003 36313 Female FL Levy 2002, 2003 36316 Female GA Long 2002, 2003

13

I conducted surveys from the air to increase my detection of VHF-tagged birds. I flew in

single-engine, fixed-wing Cessna 172 and 182 aircrafts affixed with strut-mounted two-element

H-antennas (Telonics Inc.) at ground speeds of about 175-200 km/hr and altitudes of 300-700 m.

Two observers each monitored their own programmable scanning receiver at 164.000-167.999

MHz (R-4000, Advanced Telemetry Systems, Inc.), which had been programmed with half of the

kite frequencies to reduce the length of the scan cycle. By using two receivers, the plane covered

less than 10 km per scan cycle, substantially improving the probability of detection. Once a

radio-tagged bird was detected from the air, the pilot flew in a circle so I could listen for the

signal’s highest amplitude. I then recorded the heading of the plane to later calculate the bearing

to the signal, the signal strength (weak, medium, strong), and the plane’s latitude and longitude in

decimal degrees with a Global Positioning Systems (GPS) receiver (Garmin GPS 12-XL with an

external windshield-mounted antenna). This was repeated one or two more times throughout the

flight. I can only estimate that the kite was within a distance of 100 km because the exact

distance from the plane to the bird could not be determined. Later, I mapped the recorded

bearings and estimated the bird’s location (White and Garrott 1990). The precision of the

triangulated location most likely fell within a radius of 3 km of the actual location.

I used the scanning receiver to listen for VHF radio-tagged kites while driving throughout

the study area with a dipole whip antenna affixed by a magnet to the top of the vehicle. I marked

the latitude and longitude of my position once a radio-tagged bird was detected and used a

compass to determine the bearing to the bird. I then quickly drove within 1 km of the first

location to a second position to get another bearing on the bird for triangulating its approximate

location.

Migration analysis. − Ι critically examined satellite-derived locations for each bird from

ARCI’s historical (2000 and 2001) and present data (2002 and 2003) to confirm that the distance

14

traveled since the previous location was plausible in the given time span (data processing by

Service Argos produces incorrect locations 1-2% of the time). Obviously erroneous locations

were removed, as well as locations recorded within 30 minutes of the previous one (< 15 %),

increasing the independence of sequential locations.

The satellite data reports included the accuracy of the satellite fix, which is labeled

Location Class (LC). There were seven possible LC’s, ranked here with their error associations:

Z (failed location), B (unknown), A (unknown), 0 (> 1500 m), 1 (< 1000 m), 2 (< 350 m), and 3

(< 150 m). Each satellite-derived location had about a 67% probability (1 standard deviation) of

being within the error radius for the stated location class. I used only LC 0 through 3 for the

migration analyses.

I defined the total migration route for each bird as the distance from the first location

where it demonstrated continual southbound movement in the United States to the initial location

on its winter range in South America. I plotted all migratory routes from 2000 to 2002 on the

Environmental Systems Research Institute, Inc.’s (ESRI) map of the world in ArcView GIS. I

then divided the entire migration route into 12 geographic regions, or migration sections (Fig. 2.2,

Table 2.2), extending from the southern tip of Florida to winter locations in south-central South

America. Although subjective, sections were delineated to define discrete, relatively linear

portions of the migration route. Analyses of migration rates and stopover behavior were based on

these 12 geographic areas. To obtain the length of each of the 12 migration sections, I used

ArcView’s ruler function, aligning the ruler along the center of the migratory route defined by

satellite-derived Swallow-tailed Kite locations, and recording each migration section’s length.

All distances were measured in kilometers.

All migration routes from 2000 to 2003 were plotted in ArcView. Using the Animal

Movement extension (Hooge and Eichenlaub 1997), I calculated the sum of successive distances

15

Figure 2.2. The 12 migratory sections partitioned along the Swallow-tailed Kite’s migratory route used in the migration rate analysis.

16

Table 2.2. Length and descriptions of 12 migration sections used for the analysis of Swallow-tailed Kite migration. These sections define the Swallow-tailed Kites’ migratory pathway from the southern tip of Florida through the southern-most winter regions in South America

Section Description Length (km) 1 Southern Florida to Mexican coast 770

2 Mexico and Belize 640

3 Honduras 450

4 Nicaragua 420

5 Costa Rica and northern one-third of Panama 400

6 Southern two-thirds of Panama 500

7 Western Columbia (west of Andean divide) 620

8 Southwestern Columbia, northeastern Ecuador, northern Peru (east of Andean divide)

880

9 Northwestern Brazil 815

10 Northern Bolivia and western Brazil 850

11 Southeastern Bolivia and western Brazil 550

12 Eastern Paraguay and southern Brazil 550

Total migration

7445

17

between all satellite locations. The satellite reports from Service Argos, Inc., provided the date

and time for each location, allowing me to measure the elapsed time between each individual’s

successive locations.

For each of the 12 sections, I quantified several parameters describing migration rate and

movement patterns. These included the movement distance (cumulative distance between

successive telemetry fixes within a section), progress distance (direct line between the kite’s first

location and last location within a section), and duration (time between the first and last location

within a section) for each bird (Fig 2.3). I created a stopover index by obtaining a ratio of the

movement distance to the progress distance for each section (Fig 2.3). For example, if a

kite moved linearly through a section, it would have a stopover index of approximately 1.0. A

kite that wandered widely within a section would have a large movement distance relative to its

progress (stopover index >> 1).

In addition to calculating duration between known satellite fixes, I also estimated the total

duration in each section. To do this, I calculated the elapsed time between the last point in the

previous section and the first point in the successive section and estimated the proportion of that

time difference to the section boundary (Fig. 2.3). That proportion was then added to the time

associated with the last fix in the previous section. This produced an approximation of the date

and time kites entered and left a section.

Three measures of migratory rates (collectively referred to as rates of travel) were

calculated within each section from the above parameters (Fig. 2.3). Movement rate was the

movement distance divided by the elapsed time between the first and last location within a

section. The progress rate resulted from the progress distance within a section divided by the

elapsed time between the first and last location within that section. The net migratory rate was

calculated by dividing the total section length (Table 2.2) by the estimated section duration. Not

18

Section boundary

Section boundary

A

B

C

Estimated arrival

Estimated departure

Figure 2.3. Example of the distances used in the calculation of the four movement variables used to estimate stopover of Swallow-tailed Kites. Movement rate calculated by the distance between successive locations within a section (A) divided by the time duration between them. Progress rate calculated by the distance between the first and last location (B) within a section divided by the duration between them. Stopover index calculated from the ratio of the movement distance (A) divided by the progress distance (B). Net migration rate calculated by the section length (C, see Table 2.2) divided by the estimated duration a kite spent in the entire section.

19

all birds produced a satellite fix in all sections. Thus, a kite only produced measurements for a

migratory section if it had at least two fixes within the section boundaries. However, all birds

produced a net migration rate for every section (whether they produced a satellite fix in a section

or not, they still passed through that section) because an arrival and departure was estimated for

all sections.

I chose four movement variables: progress rate, movement rate, net migration rate, and

stopover index to quantify stopover in Cuba and the Yucatan. Using a one-way ANOVA, I

compared differences among the 12 sections for each of these four variables. The Dunnett’s test

was applied a posteriori to test the specific prediction that migration rates and stopover index in

other migration sections differed from those in the Yucatan (section 2, which served as the

reference in these tests) with regard to each movement variable. A two-way ANOVA was then

used to determine if there were differences between males and females for the four movement

variables described above.

Because of the irregular activity of satellite transmitters, not all birds produced a

telemetry location in every section. Furthermore, some birds died en route. Thus, there were

variable sample sizes per section, and a repeated measures analysis was not possible. However,

with only 29 southbound migrations, using only a single fix per bird would have been insufficient

for analysis. Thus, I analyzed all locations for all birds although this may have resulted in some

non-independence among sections. This statistical analysis should be considered exploratory,

and Figs. 2.4-2.6 and 2.8 allow readers to make their own qualitative assessment of migration

rates.

The exception to this was the net migration rate. All individuals produced an estimated

duration for all sections. Thus, a repeated measures ANOVA was performed on the net migration

rate data to ascertain if there were differences in net travel rates among sections. This analysis

20

was performed with data from sections 1-10 to include the maximum number of migrating kites

(n = 9 in 2002, n = 8 in 2003, n = 20 in 2000-2003) through the location of the northernmost

winter ranges.

All tests were repeated three times, once each for year 2002, 2003 and all years (2000 to

2003) combined. I used a paired t-test to compare migratory behavior between years by pairing

the mean of each migration variable for each of the 12 migration sections from 2002 (n = 14

kites) with the corresponding section in 2003 (n = 9 kites). I also used a paired t-test to compare

each migration variable for the seven Swallow-tailed Kites that had live transmitters in 2002 and

again in 2003 to determine if individual kites were congruent in their migration patterns from

year to year (variables paired by section between years).

Habitat Analysis. − To determine what habitats Swallow-tailed Kites were occupying

while in the Yucatan, I examined all kite locations in relation to digital satellite imagery. I

extracted the three most accurate Location Classes (1-3) of the satellite fixes from 1996 to 2003,

and combined these with the locations of VHF-tagged birds found in the Yucatan and compiled

them into one location database. This coordinate file was split into two parts to analyze Mexico

(n = 85 kite locations) separately from Belize (n = 34 kite locations) because I had different GIS

classification schemes for each country, and any resulting management decisions are likely to be

country-specific.

Satellite imagery combined with GIS technology has proved to be instrumental in the

production of detailed and accurate habitat-use maps (Palmeirim 1988). Digital habitat layers

were supplied by Amigos de Sian Ka’an for Mexico, and by Programme for Belize for Belize.

Both GIS layers were created with LANDSAT imagery with a 30-m spatial resolution and given

land cover classifications by the respective organizations. I then converted these raster files to

vector files to display the land cover habitats as polygons. I overlayed the coordinate locations

21

onto the habitat layers in ArcGIS. I used an equal number of random locations within the study

areas of Quintana Roo and Belize, created from Microsoft Excel’s random number generator.

These locations were also overlayed onto the GIS habitat layers. All kite and random locations

were buffered with a 1500-m radius circle to account for the error radius of the least accurate

satellite fixes (LC 1; Argos 1996). These buffers also take into account that a bird capable of

rapid movements probably bases its foraging decisions on broad landscape features rather than

the vegetation at its immediate location. I tabulated habitat areas within each of the buffers (kite

and random) to acquire the relative proportions of each habitat classification within each circle.

Finally, the total area of each habitat class in Quintana Roo, Mexico and mainland Belize was

calculated to determine the proportion of each habitat type available in each country.

I acquired 85 Swallow-tailed Kite radio-tracking locations throughout Mexico (the states

of Quintana Roo, Yucatan, and Campeche). However, to determine habitat use, I only compared

the VHF and satellite locations (n = 59) to random locations within the state of Quintana Roo.

Satellite fixes were localized in Yucatan, but broadly distributed in Quintana Roo. Thus, the

country-wide habitat classification for Peninsular Mexico would have included a large, unused

area (based on the observed distribution of telemetry fixes). For this reason, I only used Quintana

Roo in the habitat analysis because it had the greatest concentration of locations within a defined

boundary. There were ten habitat classes in the GIS habitat classification for Mexico, which I

consolidated into six habitat classes based on their structural similarities (e.g. lowland savanna +

coastal savanna = savanna; Table 2.3).

I performed t-tests to compare the average proportion of each habitat type at Swallow-

tailed Kite locations to the average proportions at random locations. I also performed t-tests to

determine whether the average proportion of each habitat type at kite locations matched the

known availability of that habitat country-wide (comparing sample mean to hypothesized value;

22

Table 2.3. Ten GIS habitat classes* available for Mexico and the six habitat classes used in the habitat analysis.

GIS habitat classes Habitat classes for analysis

High and medium forest High and medium forest

Low forest Low forest

Miscellaneous vegetation

Mangrove Low deciduous forest

Miscellaneous vegetation

Disturbed areas Disturbed areas

Agriculture Agriculture

Areas w/out vegetation

Open water Urban

Areas w/out vegetation

*Habitat classes categorized by Amigos de Sian Ka’an,Crepusculo #18 ESQ, Amanecer, Residencial Alborada, Manzana 13 SN 44, CP 77506 Cancun, Quintana Roo, Mexico.

23

Sokal and Rohlf 1995:169-175). Furthermore, I compared the habitat proportions used by males

and females in Quintana Roo as well as throughout Peninsular Mexico. Finally, I compared the

diversity of habitat as sites used by kites to the habitat diversity at random sites. I used the

reciprocal of the Simpson’s index, also known as Hill’s N2 (Krebs 1998), to quantify diversity.

This is obtained by calculating the reciprocal of the sum of the proportions of habitats Pi within

the buffer circles squared (1/ ∑Pi2).

To assess the degree to which there were consistent individual differences in habitat use

among kites, I used the kites that had more than one telemetry fix (13 in Quintana Roo, 16

throughout Mexico) in a Model II ANOVA on each of the six habitat types. I then calculated the

variance in habitat use attributable to differences among and within individual birds.

I used principal components analysis (PCA) to describe the principal sources of variation

in habitat use as linear combinations of the original habitat proportions. First, I removed the two

least represented habitat classes (areas without vegetation and agriculture; < 6 % of used and

available habitat) for all buffers around Swallow-tailed Kite and random locations. This was

done because the variables of a PCA cannot sum to a constant value (which was the case for my

habitat proportions; sum = 1.0). Next, I conducted a PCA on the random locations alone and

scored kite locations into the PC space defined by random habitat. I could then use Student t-tests

to compare the distribution of PC scores for used habitats to random habitats (i.e., mean PC = 0).

All analyses that were performed using the Mexico dataset were repeated with the Belize

dataset. Because there were no locations on the outer cays, habitat for Belize included only

mainland Belize. The original 12 habitat classes of Belize were merged into six habitat classes

(Table 2.4) based on their structural similarities, as was done for Mexico. Moreover, urban and

water cover types (< 4 % used and available) were removed for the PCA analysis.

24

Table 2.4. Twelve GIS habitat classes* available for Belize and the six habitat classes used in the habitat analysis.

GIS habitat classes Habitat classes for analysis

Lowland broadleaf forest

Submontane broadleaf forest Broadleaf forest

Agricultural uses

Rice Agriculture

Lowland savanna Coastal savanna Savanna

Mangrove and littoral forest

Open water Wetland

Open water/wetland

Lowland pine forest

Submontane pine forest Pine forest

Urban Urban

*Habitat classes categorized by Programme for Belize, #1 Eyre Street, PO Box 749, Belize City, Belize CA.

25

All analyses were done with JMP 4.0 statistical software (SAS Institute, Inc.). Means are given

± 1 SE, and the significance level for all statistical tests was P ≤ 0.05. All probability values from

t-tests and ANOVAs performed with the six habitat classes were corrected for multiple tests using

the Hochberg adjustment for multiple comparisons (Wright 1992, Chandler 1995). Unadjusted P-

values are presented in the results, with significant values after adjustment indicated by an

asterisk.

Results

Telemetry. − I scanned for VHF-tagged birds over 4,301 km of road: 2,375 km

throughout the states of Quintana Roo and Yucatan, Mexico (1,626 km in 2002 and 749 in 2003),

and 1,926 km throughout Belize (1,370 km in 2002 and 556 km in 2003). I only found one bird

(male 6.045) from the ground throughout both field seasons (located in the Sian Ka’an Biosphere

Reserve in Mexico in 2002).

I flew 15.5 hrs in Belize and 10 hrs in Mexico in 2002 and 5 hrs in Mexico and 14.2 hrs

in Belize in 2003, a total of 44.7 hrs of flight time in search of VHF-tagged kites. In 2002, I

located six of 91 individuals that might have been alive with active transmitters (two of them

twice). In 2003, I detected five VHF- tagged individuals of 101 possible (one of them twice), all

of which were in Belize (Table 2.5). All 11 kites detected were adults, four of which were from

Florida, five from Georgia, and two from South Carolina. Five were males, five were females,

and one was unknown sex. One of the Georgia females was found in successive years in Belize

(2002 as a one-year old and 2003 as a two-year old).

Migration analysis. − I received migration data from a total of 29 satellite-tracked

Swallow-tailed Kites from 2000-2003 (17 females and 12 males; Appendices A-C). Twenty-six

of the 29 birds with satellite transmitters traveled through the study area, whereas one bird was

26

Table 2.5. Fifteen locations of ten individual VHF radio-tagged Swallow-tailed Kites detected in Mexico and Belize, 2002 and 2003.

Bird ID (frequency) Age Sex

State tagged

County tagged

Date found

Country found Longitude Latitude

6.086 Adult Male FL Levy 8/1/02 Belize -87.97 19.63 6.086 Adult Male FL Levy 8/2/02 Belize -87.90 19.46 4.155 2yr Unknown SC Georgetown 8/14/02 Belize -88.47 18.06 6.168 Adult Female FL Levy 8/14/02 Belize -88.85 17.54 6.045 Adult Male FL Levy 8/20/02 Mexico -87.98 17.93 6.254 Adult Female FL Polk 8/20/02 Belize -88.90 17.88 6.045 Adult Male FL Levy 8/21/02 Mexico -88.73 15.95 6.254 Adult Female FL Polk 8/21/02 Belize -88.58 16.20 6.234 1yr Female GA Long 8/23/02 Belize -88.47 16.83 4.846 Adult Female GA Brantley 8/15/03 Belize -88.38 17.68 6.234 2yr Female GA Long 8/15/03 Belize -88.60 17.80 5.545 1yr Male GA Bryan 8/18/03 Belize -88.39 17.63 6.193 1yr Male GA Wayne 8/18/03 Belize -88.30 17.65 6.193 1yr Male GA Wayne 8/19/03 Belize -88.35 17.08 4.708 Adult Male SC Charleston 8/20/03 Belize -88.30 17.42

27

assumed to have died just shy of Mexico’s northern coast, and the other bird flew around the Gulf

of Mexico by-passing the Yucatan two years in a row (Appendix B).

Based on data from 2000 to 2003, the median departure date for Swallow-tailed Kites

leaving Florida was 10 August (Table 2.6). Total migration duration was variable due to

differences in exact routes of individual birds. The average migration distance from the southern

tip of Florida to wintering sites was 7751.1 km (range: 8947-5901 km); the average total

migration duration was 1904.1 hr (approximately 79 days). Swallow-tailed Kites averaged 4.4

km/hr as an overall movement rate throughout their entire migration.

Swallow-tailed Kites did not migrate at constant rates along their migration route.

Movement rate (F = 11.02, P < 0.01 in 2002; F = 5.40, P < 0.01 in 2003; F = 13.23, P < 0.01 in

2000-2003), progress rate (F = 11.70, P < 0.01 in 2002; F = 4.78, P < 0.01 in 2003; F = 12.98, P <

0.01 in 2000-2003) and net migration rate (F = 13.74, P < 0.01 in 2002; F = 5.57, P < 0.01 in

2003; F = 18.18, P < 0.01 in 2000-2003) varied among migration sections (Figs. 2.4-2.6, and see

Table 2.7 for sample sizes). The repeated measures analysis for these birds for the estimated

net migration rate again showed variation in migration rates among sections (F = 10.79, df = 8, P

< 0.01 in 2002; F = 3.09, df = 7, P < 0.01 in 2003; F = 8.39, df = 19, P < 0.01 in 2000-2003).

Swallow-tailed Kites had the highest travel rates over water and Cuba (section 1; Fig 2.4-

2.6.). Of the 29 kite migrations, 13 (45%) missed Cuba entirely. Six kites passed over at least a

portion of the island without providing a satellite location (Fig. 2.7). Some of them may have

landed, although the brief period they were over land suggested that they remained in the air the

entire time. The ten birds that did yield satellite locations in Cuba spent an average of only 35 +

16.3 hr on the island.

Conversely, Swallow-tailed Kites slowed down on the Yucatan Peninsula, and moved

through the section slower than adjacent sections of Cuba/over-water and Honduras (Fig. 2.4-

28

Table 2.6. Migration arrival timetable for Swallow-tailed Kites migrating from Florida to their winter range, 2002, 2003, and 2000-2003 combined. Section # correspond with Table 2.2.

2002 2003 2000-2003 Section # Median Range n Median Range n Median Range n

Depart Florida 1 8/10 7/17- 8/31 13 8/10 7/24- 8/24 9 8/10 7/17- 8/31 27Yucatan 2 8/13 7/19- 9/7 13 8/14 7/27- 8/26 9 8/13 7/19- 9/7 26Honduras 3 8/23 8/3- 9/21 13 8/24 8/7- 9/4 9 8/20 7/27- 9/21 27Nicaragua 4 8/25 8/5- 10/18 14 8/25 8/8- 9/6 9 8/25 8/1- 10/18 28Costa Rica 5 8/30 8/7- 10/22 14 8/27 8/10- 9/7 9 8/28 8/3- 10/22 28Panama 6 9/1 8/10- 10/24 14 8/29 8/14- 9/9 9 8/30 8/7- 10/24 28Columbia 7 9/8 8/13- 11/4 14 9/1 8/18- 9/12 9 9/6 8/9- 11/4 28Pasto Col. 8 9/14 8/17- 11/4 13 9/5 8/24- 9/16 9 9/12 8/14- 11/4 27NW Brazil 9 9/23 8/25- 10/12 12 9/13 9/1- 10/3 9 9/21 8/23- 10/12 25N Bolivia 10 10/7 9/18- 11/11 12 10/1 9/9- 11/7 9 10/4 9/9- 11/11 25W Brazil 11 10/17 9/23- 11/13 10 10/7 9/19- 11/20 9 10/14 9/19- 11/20 23S Bol/Brz 12 10/15 9/27- 11/10 4 10/6 9/22- 10/9 3 10/10 9/22- 11/18 11Arrive winter 10/23 9/29- 11/19 12 10/13 9/24- 11/20 9 10/22 9/24- 11/20 25

29

0

5

10

15

20

25

30

1 2 3 4 5 6 7 8 9 10 11 12

Section

2000 - 2003

0

5

10

15

20

25

30

2003

0

5

10

15

20

25

30

2002M

ovem

ent r

ate

(km

/hr)

*

*

* *

*

*

**

Figure 2.4. Mean (± SE) movement rate (km/hr) within 12 geographic regions for southbound Swallow-tailed Kite migrants across 3 year-categories. See Table 2.7 for section descriptions. *Indicates significant differences (Dunnett’s test) between the noted section and section 2, the Yucatan Peninsula.

30

0

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10 11 12

Section

2000 - 2003

0

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10 11 12

2003

0

5

10

15

20

25

1 2 3 4 5 6 7 8 9 10 11 12

2002

Prog

ress

rate

(km

/hr)

*

*

*

* * *

*

*

**

Figure 2.5. Mean (± SE) progress rate (km/hr) within 12 geographic regions for southbound Swallow-tailed Kite migrants across 3 year-categories. See Table 2.7 for section descriptions. *Indicates significant differences (Dunnett’s test) between the noted section and section 2, the Yucatan Peninsula.

31

0

5

10

15

1 2 3 4 5 6 7 8 9 10 11 12

Section

2000 - 2003

0

5

10

15

1 2 3 4 5 6 7 8 9 10 11 12

2003

0

5

10

15

1 2 3 4 5 6 7 8 9 10 11 12

2002*

*

*

*

**

*

*

*

Net

mig

ratio

n ra

te (k

m/h

r)

Figure 2.6. Mean (± SE) net migration rate (km/hr) within 12 geographic regions for southbound Swallow-tailed Kite migrants across 3 year-categories. See Table 2.7 for section descriptions. *Indicates significant differences (Dunnett’s test) between the noted section and section 2, the Yucatan Peninsula.

32

Table 2.7. Sample sizes of Swallow-tailed Kites used in migration analyses of four migration variables in 12 migration sections in 2002, 2003 and 2000-2003 combined.

Section Movement rate

Progress rate

Net migration rate

Stopover index

2002 1 12 12 12 12 2 12 12 12 12 3 10 10 13 10 4 10 10 14 10 5 5 5 14 5 6 14 14 14 14 7 12 12 13 12 8 12 12 12 12 9 12 12 12 12

10 11 11 10 11 11 3 3 4 3 12 4 4 4 4

2003 1 8 8 9 8 2 8 8 9 8 3 6 6 7 6 4 7 7 9 7 5 7 7 9 7 6 7 7 9 7 7 7 7 9 7 8 9 9 9 9 9 9 9 9 9

10 9 9 9 9 11 4 4 3 4 12 2 2 2 2

2000-2003 1 25 25 27 25 2 25 25 26 25 3 20 20 27 20 4 20 20 28 20 5 13 13 28 13 6 26 28 28 26 7 22 22 27 22 8 25 25 25 25 9 25 25 25 25

10 24 24 23 24 11 11 11 11 11 12 8 8 7 8

33

Figure 2.7. Southbound migration of Swallow-tailed Kites tracked by satellite from Florida through the Yucatan Peninsula in 2002 and 2003 (n = 23 migrations).

34

2.6). Kites traveled through the Yucatan at rates only 7-19% of the travel rates over water

(section 1) or through Honduras (section 3). Not only did kites move more slowly through the

Yucatan, the stopover index was higher for this section than any other on the migration route

(Fig. 2.8).

Kites arrived in Mexico as early as 19 July and as late as 7 September, and stayed on the

Yucatan Peninsula as late as 21 September (Table 2.6). Once on the Yucatan Peninsula, kites

stayed as little as 35.5 hrs and as long as 354.6 hrs (mean duration 179.2 ± 16.61 hr). The total

length of the Yucatan Peninsula (section 2) is about 640 km, and Swallow-tailed Kites averaged a

movement distance of 570.2 ± 82.47 km (range 48.1-1583.1 km). Shorter distances illustrated

that kites sometimes arrived on the Yucatan Peninsula south of the northern tip (Appendix A).

The only differences between the sexes for the four migration variables were for the net

migration rate and stopover index for the combined years. However, these differences were in

sections other than Cuba, the Yucatan, or Honduras.

Migration patterns were broadly consistant across years. Swallow-tailed Kites had

similar overall migration rates from the tip of Florida to their winter ranges in 2002 to 2003, as

well as similar departure and arrival dates. The kites did, however, have some differences in rates

of travel and stopover indices. Kites traveled faster section by section in 2003 (paired t-tests;

movement rate t = 2.51, df = 11, P = 0.03; progress rate t = 2.76, df = 11, P = 0.02), producing a

smaller stopover index than in 2002 (paired t-test; t = 2.52, df = 11, P = 0.03).

GIS Analysis for Mexico. − In Peninsular Mexico, about 75% of the habitat within kite

buffers was in high, medium, and low forests. Only the proportion of low forest was greater than

expected by chance (Table 2.8). Areas used by kites in Quintana Roo had less disturbed area and

fewer areas without vegetation than random sites (Table 2.8). These data include multiple

satellite fixes for some birds. Furthermore, there is some evidence for consistent differences in

35

0

0.5

1

1.5

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2.5

1 2 3 4 5 6 7 8 9 10 11 12

0

0.5

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Section

0

0.5

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2003

2002

2000 - 2003

** * * * * *

*

**

*

**

***

* *

**

**

* ** * *

*

*

**

* *

Stop

over

inde

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Figure 2.8. Mean (± SE) stopover index of migration within 12 geographic regions for southbound Swallow-tailed Kite migrants across 3 year-categories. See Table 2.7 for section descriptions. *Indicates significant differences (Dunnett’s test) between the noted section and section 2, the Yucatan Peninsula.

Table 2.8. Comparison of habitat use within 1,500 m of all satellite-tracked Swallow-tailed Kite locations to available habitat and to random locations in Quintana Roo, Mexico, and the comparison of the mean habitat use of individual kites to available habitat.

All kite locations (n = 59) Individual kite means (n = 14) Random All kite vs random (n = 59)Habitats Available Mean SE t P Mean SE t P Mean SE t PHigh and medium forest 0.48 0.46 0.06 0.29 0.78 0.50 0.10 0.29 0.78 0.53 0.06 0.83 0.41 Low forest 0.12 0.29 0.05 3.08< 0.01* 0.25 0.38 1.29 0.22 0.11 0.03 2.96 < 0.01* Miscellaneous vegetation 0.10 0.12 0.04 0.68 0.50 0.13 0.05 0.64 0.53 0.10 0.04 0.39 0.70 Disturbed areas 0.27 0.08 0.03 5.59< 0.01* 0.08 0.04 4.99 < 0.01* 0.21 0.05 2.10 0.04 Agriculture 0.03 0.05 0.02 0.80 0.43 0.03 0.02 0.14 0.89 0.06 0.03 0.22 0.82 Areas w/out vegetation 0.01 0.00 0.00 31.84< 0.01* 0.00 0.00 99.18 < 0.01* 0.00 0.00 1.00 0.32 * Denotes significance after Hochberg adjustment for multiple tests

36

37

habitat use among kites (Table 2.9), at least for common habitats. Thus, I performed a

comparison using only individual bird means (one data point per bird; n = 14) to the actual area.

I found that individual kites still avoided disturbed areas (Table 2.8) and areas without vegetation

(Table 2.8), but there was no significant selection for low forests.

In Mexico, sites used by Swallow-tailed Kites did not differ from random in the diversity

of habitats present (Kite 1.17 ± 0.04, Random 1.19 ± 0.04, df = 54, t = 0.30, P = 0.77). Males,

however, used habitats with a higher diversity index than females (Table 2.10). As an additional

way to assess whether kites preferred patchy or continuous habitat, I counted the number of

habitat types within kite and random buffers. I found that the distribution of the number of

habitats within kite buffers was the same as that within randomly chosen locations (1 habitat =

36, > 1 habitat = 23). Thus, there was no difference in habitat quantities within the two buffer

types (G = 0, df = 1, P = 1).

Principal component 1 (PC1) explained about 40% of the variation in habitat composition

and described a gradient from high proportions of high and medium elevation forest to high

proportions of disturbed areas (Table 2.11). PC2 explained 31% of the variation in the data and

described a gradient from a high proportion of low forest to a high proportion of disturbed

vegetation (Table 2.11). Based on PC2, kites preferred forested areas more than disturbed areas

(Table 2.12).

GIS Analysis for Belize. − In general, while Swallow-tailed Kites were in Belize, about

67% of the habitats within their buffers were broadleaf forests and agricultural areas, while pine

forest and urban zones were least represented (3%; Table 2.13). Tests between kite locations and

random locations showed that birds selected for the open water/wetland habitat (Table 2.14).

Sites used by kites had significantly less agriculture than expected (Table 2.13) before the

Hochberg adjustment.

Table 2.9. Components of variation in habitat use and diversity index by individual migrant Swallow-tailed Kites that had more than 1 location in Quintana Roo Mexico (n = 13) and Peninsular Mexico (n = 16). Quintana Roo Peninsular Mexico Variance components Variance components Habitat F P Among birds Within birds F P Among birds Within birds High and medium forest 4.37 <0.01* 0.49 0.51 4.75 <0.01* 0.51 0.49 Low forest 8.13 <0.01* 0.62 0.38 5.47 <0.01* 0.50 0.50 Miscellaneous vegetation 0.38 0.97

0.09 0.89 0.49 0.94 0.09 0.91Disturbed areas 0.23 1.00 0.06 0.96 0.07 1.00 0.01 0.99 Agriculture 0.20 1.00 0.05 0.95 0.82 0.65 0.13 0.87Areas w/out vegetation 0.00 1.00 … … 0.00 1.00 … … Diversity Index 0.30 0.99 0.07 0.94 0.36 0.98 0.07 0.93

38

Table 2.10. Comparison of the sex differences in habitat use and diversity index within 1,500 m of radio-tagged Swallow-tailed Kite locations in Quintana Roo and Peninsular Mexico. Quintana Roo Peninsular Mexico Habitats Male (n=35) Female (n=24) t P Male (n=37) Female (n=48) t P High and medium forest 0.32± 0.07 0.66±0.09 2.84 0.01* 0.30 ± 0.07 0.39 ± 0.07 0.91 0.37 Low forest 0.35± 0.07 0.21±0.08 1.26 0.21 0.33 ± 0.07 0.20 ± 0.06 1.48 0.14 Miscellaneous vegetation 0.18± 0.06 0.04±0.04

1.81 0.08 0.20 ± 0.06 0.19 ± 0.06 0.10 0.92Disturbed areas 0.09± 0.05 0.06±0.04 0.45 0.65 0.09 ± 0.05 0.10 ± 0.04 0.21 0.83 Agriculture 0.06 0.04 0.03±0.03 0.58 0.56 0.08 ± 0.04 ±0.12 0.05 0.55 0.58Areas w/out vegetation 0.00± 0.00 0.00±0.00 0.83 0.41 0.00 ± 0.00 0.00 ± 0.00 1.14 0.26 Diversity Index 1.25± 0.05 1.07±0.05 2.37 0.02 1.23 ± 0.05 1.07 ± 0.03 8.10 0.01 * Denotes significance after Hochberg adjustment for multiple tests

39

40 Table 2.11. Principal component analysis of habitat within random locations (n = 59) in Quintana Roo, Mexico. PC1 PC2 PC3 Eigenvalue 1.62 1.24 1.04 Percent variance explained 40.39 30.90 26.01

Cumulative percent variance explained 40.39 71.29 97.30

High and medium forest -0.77 -0.08 0.04 Low forest 0.23 0.60 -0.66 Miscellaneous vegetation 0.30 0.46 0.75 Disturbed areas 0.52 -0.65 -0.09

41 Table 2.12. Comparison of principal component scores from sites used by Swallow-tailed Kites to those of random locations (n = 59) in Quintana Roo, Mexico. All kite locations Random Mean SE Mean SE t P PC1 0.14 0.13 0 0.13 0.74 0.46

0.62 0.15 0 0.13 3.09 < 0.01PC3 0.27 0.58 0 0.13 1.20 0.23PC2

42 Table 2.13. Comparison of the proportions of habitats available to those within 1,500 m of locations of all migrating Swallow-tailed Kite locations and the mean proportions of individuals in Belize. All kite locations (n = 34) Individual kite means (n = 21)Habitat Available Mean SE t P Mean SE t p Broadleaf forest 0.63 0.59 0.07 0.47 0.64 0.55 0.08 0.91 0.38Agricultural 0.17 0.08 0.03 2.85 0.01* 0.08 0.04 2.59 0.02Savanna 0.10 0.15 0.05 1.09 0.28 0.21 0.07 1.71 0.10Open water/wetland 0.06 0.15 0.05 1.62 0.12 0.13 0.05 1.21 0.24Pine forest 0.04 0.02 0.02 1.07 0.29 0.03 0.03 0.24 0.81Urban 0.01 0.01 0.01 0.34 0.74 0.00 0.01 1.05 0.31* Denotes significance after Hochberg adjustment for multiple tests

43 Table 2.14. Comparison of the proportions of habitats and the diversity index within 1,500 m of migrating radio-tagged Swallow-tailed Kites (n = 34) to those of random locations in Belize.

Habitat Bird Random t P Broadleaf forest 0.59 ± 0.07 0.73±0.06 1.55 0.13 Agricultural 0.08 ± 0.03 0.13±0.04 0.82 0.42 Savanna 0.15 ± 0.05 0.06±0.03 1.69 0.09 Open water/wetland 0.15 ± 0.05 0.04±0.01 2.11 0.04 Pine forest 0.02 ± 0.02 0.05±0.03 0.95 0.34 Urban 0.01 ± 0.01 … … … … Diversity index 1.49 ± 0.09 1.35±0.07 1.19 0.24 * Denotes significance after Hochberg adjustment for multiple tests

44 Furthermore, there were minor sex differences in habitat use in Belize with males occupying open

water/wetland more than females (Table 2.15).

As was the case for Mexico, these data include multiple satellite fixes for some birds.

Furthermore, there was some evidence for consistent differences in use of submontane broadleaf

forest and open water/wetland among individual kites (Table 2.16). Thus, I performed the

analysis using only individual bird means (one data point per bird; n = 21) and comparing them to

the actual area for all available habitats. This analysis also showed that kites avoided agriculture

(Table 2.14).

In Belize, kites did not use sites with greater habitat diversity than random sites (Table

2.14), and the sexes did not differ in diversity of habitats used (Table 2.15). As done previously

with the Mexico data, I counted the number of habitat types within kite and random buffers and

used a contingency table to assess whether kites preferred patchy or continuous habitat. Kite

locations had more habitat types than random sites (G = 9.36, P = 0.02, df = 3). PC1 explained

close to 50% of the variation in habitat composition in Belize, and described a gradient from sites

dominated by broadleaf forest to a savanna and agricultural dominated landscape (Table 2.17).

Agricultural landscapes prevailed at the low end of PC2’s continuum, while savannas, wetlands,

and mangroves were at the high end (Table 2.17). Swallow-tailed Kite habitat was significantly

different from random locations for both PC1 and PC2 scores (Table 2.18).

45 Table 2.15. Comparison of males (n = 13) to females (n = 19) in habitat use and diversity index within 1,500 m of radio-tagged Swallow-tailed Kite locations in Belize. Habitat Male Female t P Broadleaf forest 0.50 ± 0.11 0.66±0.09 1.15 0.26 Agricultural 0.04 ± 0.02 0.11±0.05 1.11 0.28 Savanna 0.14 ± 0.06 0.16±0.07 0.18 0.86 Open water/wetland 0.32 ± 0.12 0.03±0.01 3.05 < 0.01* Pine forest 0.00 ± 0.00 0.03±0.03 0.68 0.50 Urban 0.00 ± 0.00 0.01±0.01 0.80 0.43 Diversity index 1.57 ± 0.18 1.39±0.10 0.95 0.35 *Denotes significance after Hochberg adjustment for multiple tests

46 Table 2.16. Components of variation in habitat use by individual migrant Swallow-tailed Kites that had more than 1 location throughout Belize. Variance components Habitat F P Among birds Within birds Broadleaf forest 6.20 0.01* 0.64 0.36 Agricultural 2.69 0.09 0.38 0.62 Savanna 1.62 0.24 0.18 0.82 Open water/wetland 110.97 < 0.01* 0.97 0.03 Pine forest 0.00 1.00 … … Urban 0.79 0.79 0.00 1.00 * Denotes significance after Hochberg adjustment for multiple tests

47 Table 2.17. Principal component analysis of habitat within random points (n = 34) in Belize. PC1 PC2 PC3 Eigenvalue 1.98 1.18 0.74 Percent variance explained 49.52 29.57 18.48 Cumulative percent variance explained 49.52 79.09 97.56 Broadleaf forest -0.68 0.13 0.02 Open water/wetland 0.33 0.58 0.72 Savanna 0.45 0.46 -0.67 Agriculture 0.47 -0.66 0.18

48 Table 2.18. Comparison of principal component scores from sites used by Swallow-tailed Kites to those of random locations (n = 34) in Belize. All kite locations Random Mean SE Mean SE t P PC1 0.86 0.34 0 0.24 2.08 0.04 PC2 1.05 0.36 0 0.19 2.62 0.01 PC3 0.53 0.48 0 0.15 1.07 0.29

49 Discussion

The 8000-km migratory route of the Swallow-tailed Kite is a narrow, repeatedly used

corridor. Because kites deviate little from this route and pass through during a narrow timeframe,

it is especially important to identify the geographic areas and habitats used most intensively to

plan the conservation of this species, which is one of the rarest raptors in the United States

(Partners in Flight 2003). My research supports three significant conclusions regarding this

migration route. First, Cuba is not a crucial stopover site for most Swallow-tailed Kites. Second,

the Yucatan Peninsula has emerged as a potentially important area of stopover and extended use

during Swallow-tailed Kites’ migration. Third, Swallow-tailed Kites are selective in the habitats

they use on the Yucatan Peninsula.

Surprisingly, 45% of the satellite-tracked kites flew past Cuba entirely, and the ones that

made landfall did not slow down or linger on the island. The apparent limited importance of

Cuba to Swallow-tailed Kites was substantiated by the smaller stopover index in relation to some

of the other migration sections. The average travel rates were faster here than for any other

segment along the migration route. The 200-km, over-water flight to Cuba may not be difficult

for such an efficient flyer as the Swallow-tailed Kite, especially when the winds are favorable. In

fact, the benefits of continuing to fly in favorable winds may outweigh any potential benefits of

stopping on Cuba. Another possibility is that Cuba lacks sufficient suitable habitat to function as

a quality stopover site.

There was considerable evidence that the Yucatan Peninsula is an important stopover site

for Swallow-tailed Kites. Rates of travel were slower in the Yucatan than the previous over water

section that included Cuba, and the slowest anywhere in Central America. Because kites crossing

the Gulf sometimes arrived well south of the northern tip of the Yucatan, my measures of

migration rate would, if anything, be biased toward faster, not slower rates.

50

The most concrete evidence for stopover in the Yucatan Peninsula was from the stopover

index (Fig. 2.8). Swallow-tailed Kites in the Yucatan had a significantly greater stopover index

than in any other migration section, which also was apparent from the sporadic backtracking and

meandering through the section rather than a continuous southward progression (Appendix A).

For an extreme example, one kite (#16081) entered Mexico south of Tulum, headed north into

Yucatan State for 3 days, arrived in central Nicaragua 10 days later, then reversed direction,

eventually (16 days later) returning to the exact same area in Yucatan State (Appendix C).

Unfortunately, this kite died or its transmitter malfunctioned in Columbia preventing me from

calculating a total migration rate or including this bird in any of the migration rate analyses for

sections 2, 3, or 4.

Swallow-tailed Kites may be stopping on the Yucatan Peninsula because they need to

replenish energy stores after a long over-water crossing. This may be especially true if the kites

by-pass Cuba due to favorable winds as they leave the Florida Peninsula. By the time they get to

the Yucatan, they would have flown at least 770 km over water. Habitat composition also may

provide optimal foraging conducive to storing fat for the rest of their migration to South America.

Because only adult kites were fitted with satellite transmitters, wandering movements in the

Yucatan presumably would not reflect unfamiliarity with the migration route.

Once on the Yucatan Peninsula, Swallow-tailed Kites were selective in their habitat use.

In Mexico, the kites used lowland forest more than expected and were found less than expected in

disturbed and unvegetated areas, revealing a preference for habitats with vegetative cover.

Principal components analysis supports this conclusion. For Belize, the results suggested little

use of agricultural areas relative to natural habitats and an attraction to open water and wetland

habitats. This was also supported by the PCA (Tables 2.17-2.18).

51

However, my results suggest that kites preferred patchy landscapes in Belize because

they used heterogeneous sites more than expected by chance. A preference for heterogeneous

landscapes was probably due to the kites’ foraging strategy. Swallow-tailed Kites fly along forest

edges to search out small animals easily gleaned from trees and aerial insects found in both fields

and forests (Meyer et al. 2004). Swallow-tailed Kites are presumed to be largely aerial

insectivores on migration (Snyder and Wiley 1976, Millsap 1987, Meyer 1998); their dependence

on certain vegetation as a feeding substrate may be minimal because their prey are airborne

(Bechard 1982).

Some studies have shown that migrant raptors use similar habitats to those occupied on

the breeding grounds (Niles et al. 1996), which, for Swallow-tailed Kites, would be low-density

forests of uneven structure interrupted by areas of fields, shrubs, and swamps (Meyer 1995).

Supporting this research, I found Swallow-tailed Kite activity on the Yucatan highest in lowland

broadleaf forest with a medium to high tree structure, interspersed with areas of agriculture and

wetland.

Over-wintering songbirds have also been shown to generalize in their use of habitats

(Lynch 1989a) and stages of forest regeneration (Green et al. 1987) in the Yucatan. Furthermore,

a study of migratory passerines in this region showed that most birds (78%) used two or more

habitats (Smith et al. 2001).

Several factors give Swallow-tailed Kites advantages over songbirds in the optimal use of

stopover sites and habitats. Soaring flight allows kites to cover areas rapidly, facilitating the

discovery of foraging habitats quickly. Their longer life-span allows for many migrations,

promoting familiarity with premium stopover sites. Adult kites also tend to be highly gregarious,

facilitating prompt and efficient detection of optimal sites. Flocking birds may transfer

52 information regarding proper orientation, favorable routes (Thake 1980), and stopover sites,

consequently leading them to the best foraging opportunities.

Swallow-tailed Kites slowed down again once they reached Panama (section 6), which

was most likely due to the geographic configuration of Panama forcing them to make deliberate

heading changes. As a result, they appeared to travel slower in my analysis than they actually

were. Another apparent decrease in travel rate occurred in western Brazil and northern Bolivia

(Fig. 2.4-2.6), but this area may serve as an extension of the ultimate winter ranges in Brazil,

Bolivia, and Paraguay. Similar decreases in migration speeds near wintering locations have been

observed in other raptors (Fuller et al. 1998, Meyburg and Meyburg 1999, Kjellen et al. 2001). In

contrast, Ellegren (1990) found that Scandinavian Bluethroats (Luscinia svecica) increased speed

near wintering destinations, and Meyburg et al. (1995) found that Spotted Eagles (Aguila clanga)

traveled faster as they approached their breeding grounds on spring migration.

Even as kites slowed down in Brazil, they continued to progress along the migration

pathway, unlike kites in the Yucatan, which deviated from the general migration course with

erratic multi-directional movements (see Appendix A). I suggest that meandering activity in the

Yucatan Peninsula may indicate that Swallow-tailed Kites explore the region to seek out

preferred habitats and foraging opportunities.

Some argue that satellite telemetry data are too coarse to use in fine-scale habitat analysis

(Blouin et al. 1999). Thus, I was conservative in using only the most accurate satellite locations

(LC 1–3) for my analysis. Moreover, by buffering each location, inaccurate assessments of

habitat selection were reduced, minimizing the probability of drawing incorrect conclusions about

habitat preferences (Rettie and McLoughlin 1999). Buffers compensated to some degree for error

in satellite telemetry locations and reflect the scale at which the highly mobile kites were likely to

53 respond to the environment. Taken together, these two precautionary measures made it possible

to confidently identify the broad habitat associations of Swallow-tailed Kites.

Mexico and Belize differed in general habitat composition. Mexico has more disturbed

areas, whereas Belize has more land in agricultural uses. In addition, Belize has two habitat

classifications not found in Quintana Roo: savannas and pine forests. Rainfall increases in the

region from north to south, which leads to increasing vegetation height southward through the

Peninsula (Paynter 1955).

The history of Maya civilization suggests that the entire peninsula was probably

deforested at one time or another (Paynter 1955). Therefore, it is unlikely that any of these

forests are pristine, although some areas have been left untouched for many years (Paynter 1955,

Lynch 1989b). Centuries of ancient Maya practices suggest that migratory birds, including

Swallow-tailed Kites, have probably adjusted to human disturbance on the Yucatan Peninsula for

thousands of years (Kricher and Davis 1989, Lynch 1989b, Whitacre et al. 1993).

Specific areas within the Yucatan stand out as particularly important to migrating

Swallow-tailed Kites and probably play a role in the migration ecology of other birds as well. A

visual inspection of the kite movement data within each country suggests that individual birds use

the Sian Ka’an Biosphere Reserve in Mexico and, especially, a 100-km-wide corridor

immediately adjacent to the Reserve, most intensively. This well-defined corridor extends

southward through the length of Belize and, with the exception of the Maya Mountains in south-

central Belize, it is fairly uniform in geology and topography (Lynch 1989b).

My satellite data illustrate that migrating Swallow-tailed Kites arrived on the Yucatan

Peninsula anywhere along its eastern, northern, or even western shoreline (Appendix A). Those

that arrived on the northeastern coast came ashore in areas undergoing the most rapid tourism

development on the Peninsula and moved quickly either west or south. The kites that headed

54 west to the state of Yucatan lingered and concentrated in a relatively small area before turning

southward. During field observations, I noticed similarities in the mix of cattle ranches and

hénequen (Agave spp.) plantations, which occupy one-quarter of the Yucatan State (Paynter

1955), to indigenous ejidos, or traditional low-intensity collective farms, in Quintana Roo. Both

have a heterogeneous structure of forest patches interspersed with shrubland, fields, and/or

wetlands, which may explain the kites’ intensive use of these two disjunct areas. Another

difference between the two states is the forest composition, mainly deciduous forests in Yucatan

and evergreen forests in Quintana Roo (Paynter 1955).

When leaving the Yucatan Peninsula, many Swallow-tailed Kites departed from Punta

Gorda, the most seaward point in southeastern Belize. The combination of satellite data, visual

observations of kettling kites heading southeast (L. Zeoli, pers. comm.), and VHF-signals

detected at sea in this area imply that some Swallow-tailed Kites fly over the Bay of Honduras,

possibly using the cays as they proceed south (Fig. 2.7 and Appendix A).

Telemetry by airplane proved was the most effective way to locate VHF radio-tagged

kites due to the large detection range (up to 100 km) and limited roads in the study area. I was

surprised to find only 11 individuals (5.7%) out of the 192 kites for which I scanned in two years

of telemetry surveys. Louisiana kites, however, may not pass through my study area. When

Louisiana are not considered as part of the sample, the number of individuals that could be

detected is reduced from 192 to 120, increasing my detection rate to 9.2%. Removing yearling

birds (many of which probably had already died) from the sample further increases my detection

rate to 14.5% (n = 76 birds). Daily flights well into September would have been necessary to

improve my VHF-detection rate.

The methods I used to analyze the movements and quantify stopover behavior of

Swallow-tailed Kites were effective. This methodology could be applied to other species with

55 similar stopover behavior on larger spatial scales than passerines (which have been the focus of

nearly all studies of stopover ecology). Although raptors have been reported to use stopover sites

(for resting and foraging) comparably to passerines and shorebirds (Niles et al. 1996), their use of

the landscape at a larger scale, as demonstrated in this study, is distinctive.

Conservation. − Natural habitats in the Yucatan Peninsula face threats from coastal

development, aquaculture development, population growth, and the decline of traditional farming

practices in favor of conversion to intensive, large-scale agriculture (Lynch 1989a, Merediz

2003). These changes could have a significant impact on the future of the Swallow-tailed Kite.

In the tropics, the potential loss of raptor species (such as the Swallow-tailed Kite) is of special

concern because of the impact it can have on trophic levels preceding it (Bierregaard 1995).

I suggest that the Swallow-tailed Kite could serve as a compelling flagship species for

conservation of natural habitats in the Yucatan. The kite is an excellent focal point for

conservation and education efforts for several reasons. First, they are relatively conspicuous,

facilitating peoples’ involvement and interest for their protection. Second, even though kites

associate with forested habitats, they coexist with traditional forms of human land use, which can

directly connect a variety of human interests to conservation plans. Third, the fact that Swallow-

tailed Kites are long-distance migrants makes them an international resource of global concern.

Furthermore, my results suggest that the Yucatan is important to kites, thus, these areas may be

compelled to promote human practices beneficial to the Swallow-tailed Kite. Kites can provide

leverage in protecting the diverse natural areas they use on the Yucatan, while protecting other

species that use the areas as well.

Recommendations for further research. − This research highlights the need for additional

investigation of Swallow-tailed Kite ecology in the Yucatan Peninsula. An increase in aerial-

telemetry combined with a longer field season would have allowed me to locate more VHF-

56 tagged Swallow-tailed Kites. Because other satellite telemetry studies have found differences in

migration patterns between adults and juveniles (Ueta et al. 2000, Kjellen et al. 2001, Meyberg et

al. 2001, Thorup et al. 2003), studies on Swallow-tailed Kites should be extended to include

satellite research on juvenile birds to determine differences in stopover behavior and threats

between the age classes.

Because stopover sites are used for respite and to refuel, it would be beneficial to find

exactly where Swallow-tailed Kites rest and what they are eating. Early morning and late

evening aerial surveillance of VHF-tagged birds, (when the kites are most likely perched),

referenced to the most accurate night-time, satellite-derived locations would increase the chances

of finding roost sites. It is possible we could discover historical communal roosts, places many

kites have used for years, similar to the large pre-migratory roost in Florida (Meyer 1998) and on

the winter range in Brazil (K. Meyer, pers. comm.). These geographic locations should have the

highest priority for protection.

It would be advantageous to follow and observe individuals or groups of migrating kites

to ascertain their exact behaviors and food sources in the study area. Local residents report

seeing Swallow-tailed Kites feeding on flying insects such as dragonflies and locusts in the same

locations year after year (B. MacKinnon, pers. comm.). A prey-based study would identify

insects and other species most important to the diet of migrating kites and could assess

abundance, reliability, and limiting factors for prey species. A more intensive investigation in the

Sian Ka’an corridor would also contribute to our understanding of Swallow-tailed Kite

conservation needs in this critical stopover region.

Beyond the Yucatan Peninsula, the migratory rate data and methodology developed for

my study can identify other constriction points and important locations along the entire migratory

route of the Swallow-tailed Kite. This would be the first step in targeting and prioritizing sites in

57 need of conservation planning and management action. The decrease in travel rate in the narrow

isthmus of Panama (section 6), the high elevation passage through the Andes Mountains in

Columbia (section 8), and areas of protracted use in northwestern Brazil and northern Bolivia

(sections 9 and 10) are examples of the most obvious locations worth examining given the present

state of our knowledge and analyses.

Chapter III

Habitat Associations of Swallow-tailed Kites During Three Phases

of Their Annual Cycle

Introduction

The population decline of Swallow-tailed Kites is substantial and merits action (Meyer

1995). Although it is hard to pinpoint the specific causes of decline, the loss of nesting habitat in

bottomland forests and foraging habitat such as prairies and wetlands in the southeastern U.S. is

traditionally cited as a cause (Cely 1979, Robertson 1988, Meyer 1995). Because they are

migratory, Swallow-tailed Kites could also be facing dangers along their lengthy migration route

from the U.S. to winter ranges in parts of Bolivia, Brazil, and Paraguay. Unfortunately, many

aspects of their habitat selection and habitat availability throughout their annual cycle and

geographic range are unknown.

Swallow-tailed Kites use habitats on a global scale. Over the course of a year, kites find

and select appropriate habitats along a narrow, 8000-km long corridor (See Fig. 2.1). This poses

challenges for the kites as well as for conservation biologists trying to pinpoint the factors that

limit kite populations. A limiting factor is by definition something that can cause a species to

decline, or prevent it from increasing, such as predation, limited food supply, limited nest site

requirements, parasites and pathogens, inclement weather, pollution, and hunting (Newton 1998).

Furthermore, many of these threats are exacerbated if populations do not have access to suitable

habitat. A species’ abundance, in general, depends on the amount of suitable habitat available

within its range (Newton 1998).

59 Swallow-tailed Kites spend about 38% of the year on the breeding grounds, 26% on

southbound migration, 22% on winter ranges and the remaining 14% of the year on northbound

migration (Meyer 1995). The highest proportion of the Swallow-tailed Kite’s annual cycle is

spent in transition from one continent to another. Most research on the Swallow-tailed Kite (and

other birds as well; review in Leu and Thompson 2002) has been conducted on the breeding

grounds, a location where kites spend only about one-third of their annual cycle (Meyer 1995).

Therefore, habitat availability and the other limitations Swallow-tailed Kites face during the non-

breeding season the other two-thirds of the year need to be examined further.

Studies of habitat selection throughout the range of a long-distance migrant are rare.

Fortunately, it is now possible to obtain large-scale habitat information inexpensively using

remotely sensed data (LaPerriere et al. 1980). This makes it possible to map global migratory

pathways and to study habitat associations on a range-wide scale. Combined with Geographic

Information Systems (GIS), remotely sensed data have been used to develop habitat suitability

models (LaPerriere et al. 1980, Green et al. 1987, Hogdson et al. 1988) during breeding and non-

breeding seasons as well as detailed wildlife distribution maps (Lyon 1983, Austin et al. 1996).

With the combination of continuous satellite tracking and remotely sensed habitat data,

the Swallow-tailed Kite can provide a useful model for determining the seasonal importance of

habitat selection on a hemispherical scale. Survival and population growth are based on the

interactions of complex events throughout all stages of the annual cycle (Gill et al. 2001, Webster

et al. 2002). However, some habitat challenges and limitations may be significantly more

prevalent during one season than another. For example, during the breeding season, Swallow-

tailed Kites select habitats based on quality nest sites. Furthermore, stopover site habitat,

especially after crossing large geographic barriers such as oceanic expanses (Moore and Kerlinger

60 1987, Moore et al. 1990), are selected based on their capacity to provide rest and quick

replenishment of food and water (Nature Conservancy 2002).

On the winter ranges in Bolivia, Paraguay, and Brazil, Swallow-tailed Kites encounter

direct resource competition not only with other migrant kites from the U.S., but also other

migrants from north of the equator, the South American breeding Swallow-tailed Kites (yetapa

subspecies), wintering flocks of Mississippi Kites (Ictinia mississippiensis), and wintering and

breeding Plumbeous Kites (Ictinia plumbea) (K. Meyer, pers. obs.). Undoubtedly, habitats on

winter sites must provide a sustainable food-base for birds to maintain themselves during non-

breeding times (Sherry and Holmes 1996). The winter season, or non-breeding season, is often

regarded as the most limiting period of the year partly because of the high rates of deforestation

in the tropics (review in Rappole and McDonald 1994), where most Neotropical migrants spend

the non-breeding season.

Which season if any, during the annual cycle do Swallow-tailed show the greatest habitat

selectivity? Are kites choosing for certain habitats along their route, and are the patterns of

choice similar among seasons? To approach these issues I quantified whether the birds associated

with habitats significantly different from what was available, and whether this selection was more

pronounced during one season than others. The objectives of this study were to assess if 1) kites

use similar habitats throughout the annual cycle, 2) if certain habitats are used more than others

and 3) if kites are more selective during one phase of the year than others.

Methods

I selected Swallow-tailed locations from three major phases of their annual cycle:

breeding, stopover, and wintering (Figs. 3.1-3.3). These locations were overlayed onto a globally

classified, digital land cover map. Within the breeding region, 477 nest locations were chosen

throughout the Florida peninsula (n = 386) and southeastern Georgia (n = 91), an area

61

Figure 3.1. Swallow-tailed Kite nest locations (n = 477) and the area defined as available for the breeding season in the hemisphere-wide habitat analysis.

62

Figure 3.2. Swallow-tailed Kite telemetry locations (n = 114, from 29 individuals) and the area defined as available for stopover used in the hemisphere-wide habitat analysis.

63

Figure 3.3. Swallow-tailed Kite telemetry locations (n = 440 from 14 individuals) and the area defined as available for the winter season in the hemisphere-wide habitat analysis.

64 representing roughly two-thirds of the U.S. breeding range (Fig 3.1). Nest coordinates were

accumulated from 1988-2003 during the nesting months of March-July.

Coordinate locations for Swallow-tailed Kites during stopover and winter seasons were

obtained from conventional VHF telemetry and satellite telemetry. Birds with VHF transmitters

were located with hand-held, roof, or strut-mounted antennas from the ground or by plane (see

Chapter II for details). By obtaining at least two bearings on the kite from separate positions

within a 5-min span, coordinates were later acquired by triangulating the bearings on a map.

Coordinate locations from birds with platform transmitter terminals (PTTs) were obtained by the

polar orbiting satellites’ detection of the birds’ unique signal (Argos 1996). This satellite

information was processed by Service Argos and sent to me as a report via e-mail. Each bird

produced about four satellite fixes per day, of which 0-2 were accurate enough to use in this

analysis. I used only the three most accurate Locations Classes (LC 1-3) out of seven possible

LCs ranked here with their error associations: 1 (<1000 m), 2 (<350 m), and 3 (<150 m). Both

VHF and satellite-telemetry locations were obtained between the hrs of 0830 and 1900 to increase

the probability that kites were foraging at that time.

I used the Yucatan Peninsula to represent the stopover region, specifically, the Mexican

states of Quintana Roo, Campeche, and Yucatan, plus the country of Belize (see Chapter II for

evidence of stopover in this area Fig. 3.2). The Swallow-tailed Kite locations came from a total

of 102 satellite-derived and 12 VHF-detected locations from 35 southbound migrating Swallow-

tailed Kites tagged in Georgia and Florida. Most locations (n = 106) were obtained from 20 July

to 10 September during the years 2002 and 2003, in addition to five from 1996 and three from

1998.

Locations within the winter range in South America were derived from satellite-tagged

birds captured in Georgia and Florida from 2000 to 2003. The winter ranges of each bird (n = 14)

65 were defined as those fixes between the last location of continuous southbound movement to the

first location of continuous northbound movement. Most of these locations were close to the

borders of Bolivia and Paraguay in western Brazil, while the rest were on the other side of the

border in eastern Bolivia and Paraguay (Fig. 3.3). There were 220 satellite-derived kite locations

(n = 9 individuals) in Brazil, 75 (n = 4 individuals) in Bolivia, and 145 (n = 2 individuals) in

Paraguay (some birds’ winter ranges spanned multiple countries). The 440 winter locations were

acquired as early as 27 September to as late as 28 January in 2000-2004.

Nests and foraging locations within the three study regions were encircled with a 5-km

radius buffer, which creates a circle with a 10-km diameter comparable to the average activity-

range size of a breeding Swallow-tailed Kite (Meyer and Collopy 1995). Meyer and Collopy’s

study found that the maximum foraging range of a nesting Swallow-tailed Kite spanned 20 km on

its longest axis. I next selected the area that would define “available” habitat within each region.

I generally defined this with a minimum convex polygon connecting the outer-most nest and

foraging locations, and then extended the area 10-km beyond the outer-most points. The 10-km

extension is again based on the average activity range of a Swallow-tailed Kite (Meyer and

Collopy 1995).

The available area used for the nesting locations included peninsular Florida, north to

South Carolina, and west to a line from Screven County, Georgia to Liberty County, Florida (Fig

3.1). The coastline defined the eastern and southwestern boundary of the available breeding area.

This totaled an 187,635-km2 available area tested in the breeding habitat selectivity analysis.

The stopover area available to Swallow-tailed Kites included the Mexican states of

Quintana Roo, Yucatan, and part of Campeche, plus the country of Belize. The western boundary

for the available area was a line connecting the southwestern-most corner of Belize, across

66 Guatemala and to the western-most satellite-derived location within the state of Campeche,

Mexico (Fig. 3.2). The total available area within the stopover designation totaled 177,995 km2.

The available area in the winter range in South America was defined by a minimum

convex polygon around all of the 440 foraging kite locations (Fig 3.3). The location of this

rectangular polygon of available area spans roughly 1830 km diagonally from northern Bolivia to

southern Paraguay. The western boundary reaches into Bolivia and Paraguay about 250 km from

the Brazil border, and the eastern boundary extends into Brazil about 400 km. This winter area of

1,165,353 km2 was the largest available area of the three kite seasons.

I selected the newly complete Global Land Coverage (GLC2000) created in 2002 by the

European Commission’s Joint Research Centre as part of a project called Global Environment

Information Systems (GEIS; GLC 2003), to use as my continuous land cover database. This

remotely sensed coverage was based on SPOT-4 VEGETATION VEGA2000 dataset, which is a

satellite imaging system that provides 1020-m resolution images produced by the French

organization Systeme Pour l’Observation de la Terre (SPOT) (Bolstad 2002). The coverage is

displayed under the Interrupted Goode’s Homolosine projection (Goode 1925), a "lobed" equal-

area projection that displays areas linearly proportional to the corresponding region on the sphere

(Fig. 3.4) and reduces some forms of distortion when displaying the entire earth surface (Bolstad

2002, Furuti 2003). GLC2000 is divided into 22 land cover types (18 of which are found in the

available kite areas) using the Land Cover Classification System of the Food and Agriculture

Organization (FAO) of the United Nations (Di Gregorio and Jansen 2000, GLC 2003).

I downloaded the GLC2000 from the internet (GLC 2003) as an Environmental Systems

Research Institute, Inc. (ESRI) grid, and I used Earth Resources Data Analysis System’s

(ERDAS) Imagine software to clip the three Swallow-tailed Kite regions and create vector

67

Figure 3.4. Interrupted Goode’s Homolosine projection (Goode 1925), a "lobed" equal-area projection that displays areas linearly proportional to the corresponding region on the sphere, used in the Global Land Coverage (GLC2000) for the hemisphere-wide habitat analysis.

68 (polygon) files. The vector files were then brought into ESRI’s ArcMap GIS program where the

associated kite locations, buffers, and available area files were overlayed to intersect with the

GLC2000 land cover. This allowed me to tabulate the area for each habitat classification within

the available area polygons and each kite location buffer.

Kite buffers and available area tabulations were summed and sorted into 18 habitat

classifications to calculate proportions of each habitat within kite locations and the available area

for each of the three regions using Microsoft Excel. I combined the 18 habitat classifications into

six basic land cover classifications of forest, agriculture, shrub/grassland, wetland, water, and

urban (Table 3.1). Because each of the 18 habitat classifications were not found in each of the

three study regions (e.g., the forest composition in Georgia and Florida differed from that in

Belize and Mexico), this basic land cover scheme was comparable to examine habitat structure

between the three regions. Furthermore, the physical structure of the plant communities is more

important than the actual species composition to Swallow-tailed Kites (Meyer 1995).

I used Student t-tests to compare the proportions of habitats within kite buffers to the

parametric proportions of the corresponding available habitats (comparing sample means to

hypothesized value; Sokal and Rohlf 1995:169-175). Then, because the 554 satellite-telemetry

locations during stopover and winter came from a maximum of only 29 birds, I performed a more

conservative analysis to remove the effects of non-independence. Within each of the two regions,

I combined the data to get mean habitat proportions per individual for each of the six broad

habitat classes and repeated the analysis. With these same birds, I assessed the variance

components to document differences in habitat use among birds or within birds in both areas.

When kite locations showed significant differences from any of the six broad habitat

classifications, I examined kite use for each of the original GLC2000 land cover classifications.

69 Table 3.1. Eighteen GLC2000 land covers found within Swallow-tailed Kite breeding, stopover, and winter ranges and their combination into six basic habitat classifications that were directly comparable among regions. GLC2000 land cover classifications Combined habitat categoriesEvergreen broadleaved forest Deciduous broadleaved forest Evergreen needleleaved forest Deciduous needleleaved forest Mixed forests Evergreen broadleaved swamp forest Evergreen broadleaved mangrove forest

Forest

Mosaic: tree cover/other natural vegetation Shrubland, open-closed Savannas Grasslands Sparse herbaceous or sparse shrub cover

Shrub/grassland

Wetland Wetland Croplands Mosaic: cropland/tree cover/natural vegetation Mosaic: cropland/shrub or grass cover

Agriculture

Water bodies (natural and artificial) Water Artificial surfaces and associated built-up areas Urban

70 This way I could see if there were additional distinctions of kite use within the more specific land

cover types.

Finally, I used a principal components analysis (PCA) to redescribe habitat along a

smaller number of axes that were linear combinations of the original habitat proportions. This

provided a multivariate approach to examine all the habitats combined as linear principal

components, while removing any problems with non-normally distributed data. I only used the

four most common habitats, forest, shrub/grassland, wetland, and water because the variables of a

PCA cannot sum to a constant value (which was the case for my habitat proportions; sum = 1.0).

I then scored habitat use for all three regions into the space defined by the principal components.

This permitted a direct comparison of habitat selectivity among regions. I also scored the known

available habitat for each region to examine the difference between use and available PC scores

within each region.

All statistics were run using JMP 4.0 statistical software (SAS Institute, Inc.). All

probability values from t-tests performed above were corrected for using the Hochberg

adjustment for multiple comparisons (Wright 1992, Chandler 1995). Means are expressed

throughout with standard errors, and the significance level for all statistical tests was P ≤ 0.05.

Results

The available habitat in the breeding and stopover range was largely comprised of

forested lands, whereas the winter area included more agricultural lands (Fig 3.5, Table 3.2).

Swallow-tailed Kites generally occupied forested landscapes throughout breeding, stopover, and

winter ranges, whereas urban landscapes were occupied the least (Table 3.2). Of the three

regions, overall habitat selectivity of Swallow-tailed Kites was minimal during stopover, whereas

they were most selective during the breeding season, at least for those habitats classified here

(Table 3.2).

71

0

0.25

0.5

0.75

1

Forest Wetland Cropland Grassland/shrub Water Urban

Habitat

Winter

Stopover

Breeding

Prop

ortio

n

Figure 3.5. The distribution of the available proportion of the broad scale habitats used by Swallow-tailed Kites throughout their annual cycle (breeding, stopover, winter).

72 Table 3.2. Comparison of habitat use (within 5 km of nest and satellite locations) of Swallow-tailed Kites to the proportions of the available broad-scale habitats within the breeding, stopover, and wintering area.

Breeding (Georgia and Florida, USA), n = 478 Habitat Available Kite use t P Forest 0.49 0.55± 0.02 3.19 <0.01* Wetland 0.08 0.26± 0.02 10.59 <0.01* Agriculture 0.27 0.08± 0.01 24.32 <0.01* Shrub 0.12 0.06± 0.01 11.78 <0.01* Water 0.02 0.05± 0.00 4.79 <0.01* Urban 0.03 0.00± 0.00 11.28 <0.01*

Stopover (Yucatan Peninsula), n = 115 Habitat Available Kite use t P Forest 0.85 0.77± 0.02 3.10 <0.01* Wetland 0.01 0.01± 0.00 0.07 0.95 Agriculture 0.13 0.19± 0.02 2.72 0.01* Shrub 0.01 0.02± 0.01 1.00 0.32 Water 0.00 0.01± 0.01 1.61 0.11 Urban 0.00

Winter (Brazil, Bolivia, Paraguay), n = 441 Habitat Available Kite use t P Forest 0.30 0.43± 0.02 8.95 <0.01* Wetland 0.08 0.01± 0.00 70.99 <0.01* Agriculture 0.36 0.39± 0.01 1.65 0.10 Shrub 0.25 0.18± 0.01 8.55 <0.01* Water 0.02 0.00± 0.00 35.62 <0.01* Urban 0.00 *Denotes significance after Hochberg adjustment for multiple tests

73

Nest-site selection. − Available nesting habitat was comprised of 12 of the 18 GLC2000

habitats. However, nest site buffers only contained ten of these (Table 3.3). Based on the six

broad habitat classifications that are directly comparable across the annual cycle, nesting

Swallow-tailed Kites selected sites with higher proportions of forest, wetlands, and water, and

selected against agriculture, shrub/grasslands, and urban (Table 3.3). When forest and

shrub/grassland habitats were analyzed in more detail, Swallow-tailed Kites selected needle-

leaved evergreen forests (pine forests), while they avoided both sparse herbaceous/shrub and

grassland subcategories (Table 3.3). Needle-leaved forests and agriculture formed the majority of

the available breeding area (Table 3.3).

Stopover-site selection. − The habitat available for stopover in the Yucatan was also

comprised of 12 habitats, but only nine habitats were found at kite stopover sites (Table 3.4).

Although forests dominated Swallow-tailed Kite stopover sites, the proportion of forest used by

kites at these sites was actually less than expected by chance (Table 3.4). Kites used sites with

more agriculture than expected based on its availability. A further analysis of the forested

subcategories represented in the Yucatan Peninsula revealed that kites were using both broadleaf

evergreen and needle-leaved evergreen forests less than expected by chance (Table 3.4).

Broadleaf evergreen forests cover 82% of the available stopover area.

I repeated the above analysis using mean habitat proportions for each individual (n = 25).

Kites still associated with agriculture and avoided forests (Table 3.5). In addition, they were

found around open water more than expected, although not in wetlands. Individual birds did not

differ significantly in their habitat use (Table 3.6).

Winter-range selection. − The habitat available for winter sites was comprised of 12 of

the GLC2000 habitat classifications, and Swallow-tailed Kites were found in 11 of them (Table

3.7). Swallow-tailed Kites selected for forests in winter sites, as in the case during the breeding

74 Table 3.3. Comparison of the proportion of the GLC2000 habitat classifications within 5 km of nest locations of Swallow-tailed Kites (n = 477) to the proportions of available habitats within the breeding area. Habitat Available Kite use t P Needle-leaved, evergreen 0.48 0.55± 0.02 3.27 < 0.01* Wetland/herbaceous cover 0.08 0.26± 0.02 10.59 < 0.01* Cropland 0.27 0.08± 0.01 27.74 < 0.01* Water 0.02 0.05± 0.00 4.78 < 0.01* Herbaceous cover, grassland 0.10 0.04± 0.00 13.05 < 0.01* Sparse herbaceous/shrub 0.02 0.01± 0.00 2.45 0.01* Urban 0.03 0.00± 0.00 11.28 < 0.01* Mosaic, tree cover/natural 0.00 0.00± 0.00 1.53 0.13 Broadleaf, deciduous 0.00 0.00± 0.00 2.97 < 0.01* Broadleaf, evergreen 0.00 0.00± 0.00 17.82 < 0.01* Tree cover, mixed leaf 0.00 Shrub cover, evergreen 0.00 Shrub cover, deciduous 0.00 *Denotes significance after Hochberg adjustment for multiple tests

75 Table 3.4. Comparison of the proportion of the GLC2000 habitat classifications within 5 km of satellite-tracked Swallow-tailed Kite locations (n = 114) to the proportions of available habitats within the stopover area. Habitat Available Kite use t P Broadleaf, evergreen 0.82 0.76± 0.03 2.56 0.01 Cropland 0.13 0.19± 0.02 2.72 0.01 Needle-leaved, evergreen 0.01 0.00± 0.00 5.78 <0.01* Tree cover, mixed leaf 0.01 0.01± 0.00 0.69 0.49 Wetland/herbaceous cover 0.01 0.01± 0.00 0.07 0.95 Sparse herbaceous/shrub 0.01 0.01± 0.01 0.46 0.65 Herbaceous cover, grassland 0.00 0.01± 0.00 1.17 0.25 Water 0.00 0.01± 0.01 1.61 0.11 Broadleaf, deciduous 0.00 0.00± 0.00 1.36 0.18 Urban 0.00 Mosaic, tree cover/natural 0.00 Shrub cover, deciduous 0.00 Shrub cover, evergreen 0.00 *Denotes significance after Hochberg adjustment for multiple tests

76 Table 3.5. Comparison of the proportion of the broad habitat classifications within 5km of satellite-tracked Swallow-tailed Kite locations (after combining individual locations, n = 25) to the proportions of available habitats within stopover on the Yucatan Peninsula. Habitat Available Kite use t P Forest 0.85 0.72 ± 0.05 2.70 0.01* Shrub 0.01 0.05 ± 0.03 0.92 0.37 Wetland 0.01 0.00 ± 0.00 3.10 < 0.01* Agriculture 0.13 0.23 ± 0.04 2.51 0.02* Water 0.00 0.01 ± 0.00 2.26 0.03 Urban 0.00 *Denotes significance after Hochberg adjustment for multiple tests

77 Table 3.6. Components of variation in habitat use by individual migrant Swallow-tailed Kites that had more than 1 location in the stopover area (n = 25) and winter area (n = 14). Stopover Winter

Habitat Among

birds Within bird F P Among birds Within bird F P Forest 0.18 0.82 1.17 0.30 0.34 0.64 10.14 < 0.01*Shrub 0.00 1.00 0.00 1.00 0.08 0.92 1.85 0.03 Wetland 0.00 1.00 0.00 1.00 0.40 0.59 15.47 < 0.01*Agriculture 0.15 0.85 0.91 0.56 0.37 0.64 9.49 < 0.01*Water 0.00 1.00 0.00 1.00 0.00 1.00 0.00 1.00 *Denotes significance after Hochberg adjustment for multiple tests

78 Table 3.7. Comparison of the proportion of the GLC2000 habitat classifications within 5 km of satellite-tracked Swallow-tailed Kite locations (n = 440) to the proportions of available habitats within the winter area in South America. Habitat Available Kite use t P Broadleaved, evergreen 0.13 0.38± 0.01 16.74 < 0.01* Cropland 0.26 0.24± 0.01 1.63 0.11 Herbaceous cover, grassland 0.17 0.16± 0.01 1.34 0.18 Mosaic, tree/natural 0.05 0.12± 0.01 11.29 < 0.01* Broadleaf, deciduous 0.15 0.05± 0.00 22.78 < 0.01* Mosaic, cropland/grass cover 0.05 0.02± 0.00 18.51 < 0.01* Shrub cover, deciduous 0.06 0.02± 0.00 36.90 < 0.01* Wetland/herbaceous cover 0.08 0.01± 0.00 70.99 < 0.01* Sparse herbaceous/shrub 0.02 0.00± 0.00 35.54 < 0.01* Tree cover, flooded freshwater 0.02 0.00± 0.00 25.96 < 0.01* Water 0.02 0.00± 0.00 35.62 < 0.01* Tree, flooded saltwater 0.00 Urban 0.00 Bare area 0.00 *Denotes significance after Hochberg adjustment for multiple tests

79 season (Table 3.2). Swallow-tailed Kites also avoided shrub/grasslands, but unlike the breeding

season, also avoided water and wetlands (Table 3.2). Lastly, kites were found among urban

landscapes less than expected (Table 3.2).

The forested landscapes that kites used in the winter range were a mixture of broadleaf

deciduous, broadleaf evergreen, and flooded freshwater forests. Kites selected broadleaf

evergreen forest whereas they avoided broadleaf deciduous and flooded freshwater forests (Table

3.7). Of the two shrub/grassland categories in the winter region, Swallow-tailed Kites avoided

sparse herbaceous/shrub and had no preference for grassland habitats (Table 3.7). The agriculture

category included three subcategories. Swallow-tailed Kites did not have a preference for

agriculture, whereas they did prefer mosaics of natural vegetation and trees, and avoided mosaics

of cropland and grass cover (Table 3.7).

I repeated the above analysis using means for each bird (n = 14) and I saw the same

patterns of habitat use (Table 3.8). Their selection for forested landscapes, although not quite

significant (P = 0.056), was greater than expected. Individual kites varied in their use of all

habitats except for water (Table 3.8). The greatest proportion of this variation was due to the

variation within individuals (Table 3.6).

The PCA analysis across all three regions described two principal components, which

explained about 80% of the variation in habitat (Table 3.9). The first principal component (PC1)

was a continuum from forested areas to open areas, whereas the second (PC2) described habitat

variation from wetlands (low score) to those in forests (high score; Table 3.9). I used the two PC

components to describe the habitat “space” for the kites’ entire annual cycle. For PC1, Swallow-

tailed Kites had the lowest score during stopover, and the highest score in the winter (Figs. 3.6-

3.7). Kites were most different from the available PC1 score during the winter, and most similar

80 Table 3.8. Comparison of the proportion of the broad habitat classifications within 5 km of satellite-tracked Swallow-tailed Kite locations (after combining individual locations, n = 14) to the proportions of available habitats within the winter area in South America. Habitat Available Kite use t P Forest 0.30 0.41 ± 0.06 2.07 0.06 Shrub 0.25 0.17 ± 0.02 4.31 <0.01* Wetland 0.08 0.01 ± 0.00 17.87 <0.01* Agriculture 0.36 0.41 ± 0.05 0.81 0.43 Water 0.02 0.00 ± 0.00 23.52 <0.01* Urban 0.00 *Denotes significance after Hochberg adjustment for multiple tests

81 Table 3.9. Principal component analysis of habitats at sites used by Swallow-tailed Kite (nest and satellite locations n = 1031) throughout breeding, stopover and wintering seasons. PC1 PC2 PC3 Eigenvalue 1.84 1.38 0.77 Percent variance explained 45.88 34.40 19.32

Cumulative percent variance explained 45.88 80.27 99.60

Forest -0.70 0.26 0.07 Shrub 0.44 0.34 0.80 Wetland 0.21 0.81 0.06 Agriculture 0.52 0.39 -0.60

82

-2

-1

0

1

2

-2 -1 0 1 2

Less forestMore crops

More forestLess crops

Mor

e w

etla

ndLe

ss w

etla

nd

Figure 3.6. Swallow-tailed Kite habitat use (open circles) in comparison to the available habitat (closed circles) in three regions throughout the annual cycle (Red, breeding; green, stopover; blue, winter). Points are mean principal component scores.

83

0

0.1

0.2

0.3

0.4

-1.8 -1.3 -0.8 -0.3 0.2 0.7 1.2 1.7 2.2 2.7

Winter

Stopover

Nesting

Prop

ortio

n of

kite

loca

tions

PC1 (decreasing forest--->) Figure 3.7. The pattern of forest habitat use (PC1) of Swallow-tailed Kites for breeding, stopover, and winter seasons as determined by a principal components analysis .

84 during stopover in the Yucatan (Fig 3.7). PC2 scores were lowest during the nesting season and

highest in South America during winter (Figs. 3.6, 3.8). Swallow-tailed Kite wetland use was the

most extreme from the available wetlands during the breeding season (Figs. 3.6-3.7). Over all,

the PCA analysis showed the kites to be most selective during the breeding season (Fig 3.7).

Discussion

The northern subspecies of the Swallow-tailed Kite has a complex annual cycle. Thirty-

eight percent of the year they are on their breeding grounds in the United States, 22% is spent on

wintering grounds in South America, and the remaining 40% of the year is devoted to traveling a

distance of 15,000 km or more between them (Meyer 1995). Given that Swallow-tailed Kites and

other long-distance migrants exploit the environment on a global scale, pinpointing the causes of

population declines can be a challenge. For example, Swallow-tailed Kites must select

appropriate habitats and interact successfully with predators and competitors over large portions

of two continents. Nevertheless, most habitat studies of Swallow-tailed Kites (K. Meyer, unpubl.

data) as well as songbirds (review in Sillett and Holmes 2002) have been done during the

relatively brief breeding season. Although nesting habitat plays an important role in the annual

cycle of migratory birds, these habitats may not be the most limiting throughout the year (Moore

and Simons 1989). My analysis represents the first attempt to assess range-wide habitat use of

Swallow-tailed Kites using a uniform system of habitat classification. I was able to quantify both

how the available habitats change as kites move from one region to another, as well as which

habitats the kites actually use. My analysis permits several important conclusions.

Habitats available to kites differ substantially across the annual cycle (Fig. 3.5). The

breeding and wintering grounds are the most impacted by human development. Thus, these areas

are characterized by substantial proportions of agriculture, shrub/grasslands, and other

disturbances. Stopover areas in the Yucatan, however, are still dominated by native forests, with

85

0

0.2

0.4

0.6

0.8

-3.3 -2.8 -2.3 -1.8 -1.3 -0.8 -0.3 0.2 0.7 1.2 1.7

Winter

Stopover

Nesting

Prop

ortio

n of

kite

loca

tions

PC2 (decreasing wetlands--->) Figure 3.8. The pattern of wetland habitat use (PC2) of Swallow-tailed Kites for breeding, stopover, and winter seasons as determined by a principal components analysis.

86 far less acreage devoted to agriculture and other disturbed habitats. It is clear that kites must

choose appropriate habitat against a changing matrix of availability.

The strongest pattern of habitat use by kites demonstrates a distinct association with

forested habitats. Forests represent the greatest proportion of used habitats in all three regions.

However, there are key differences in the patterns of selectivity for forests during different phases

of the annual cycle. During breeding and winter, Swallow-tailed Kites preferred forested

landscapes, while on the Yucatan, they avoided forests (in the sense that occupied sites had less

forest than expected by chance). Kites may be using the interface between forests and agriculture

where their foraging opportunities are maximized by having structural variation to detect prey

from the accessible tree canopy (Robertson 1988). Swallow-tailed Kites are known to use a

diversity of vegetation types, and are primarily regarded as being forest-edge birds (Robertson

1988 and Meyer 1995). Similarly, Greenberg (1996) found that forest patches enhance avifuanal

diversity because they attract both forest and agricultural species. It seems when kites are in less

forested landscapes (summer and winter), they prefer forests and when they are in forested

landscapes (stopover), they prefer open patches. The common feature of both situations is forest

interspersed with various open habitats (i.e., a heterogeneous landscape).

When the winter habitats were examined in their separate GLC2000 subcategories,

broadleaf evergreen forests, which make up about 13% of the available landscape in this study,

were the most important to wintering Swallow-tailed Kites. They also showed selection for a

classification labeled “mosaic of cropland, tree cover, and natural vegetation”, which most likely

describes the cerrado (savanna interspersed with open grassland) of this region. Again, the

physical structure of this habitat most likely facilitates Swallow-tailed Kites’ foraging behavior.

Other habitats on the winter range include chaco (subtropical thorn-scrub), and campos

(grassland or field; De Oliviera-Filho 1992, Davis 1993, Jahn et al. 2002). The murundus (small,

87 rounded raised landform) made by termites (De Oliviera-Filho 1992) are also present in the kites

winter range. There are over 45 termite species found in Brazil alone (Mill 1983, Gontijo et al.

1991), most of which form nuptial swarming flights at the onset of the rainy season (Mill 1983),

which could serve as a reliable food source for wintering kites. Self-maintenance is the most

important factor for winter birds (Sherry and Holmes 1996). Thus, the distribution of adequate

food sources must impact the winter habitat use of kites, as well as their survival on winter sites.

Swallow-tailed Kites were more selective in their overall habitat preference during the

breeding season than during any other time of the year (Table 3.2), meaning they significantly

avoided or selected each of the six broad habitat types. They specifically avoided agriculture,

grassland/shrub, and urban landscapes, which is not surprising due to the lack of large nesting

trees within these habitats. Given that habitat use is most different from that available, the

breeding season appears to be a critical location for the proper habitat requirements of Swallow-

tailed Kites.

I also found that Swallow-tailed Kites are only associated with wetlands during the

breeding season (Fig. 3.8). Past studies of the Swallow-tailed Kite have associated them with

freshwater swamps and wetland forests (Robertson 1988, Meyer 1995), but this is clearly a

seasonal pattern. Nest-site selection appeared to be a dichotomy between areas rich in forest and

areas rich in wetlands (Figs. 3.7-3.8). This can be explained by the distribution of nest sites

throughout the diverse habitats in Georgia and Florida. For instance, many nests in south Florida

were located within Big Cypress National Preserve and Everglades National Park, which are

areas dominated by wetlands, which include cypress swamps, mangrove swamps, and tree islands

within expanses of marsh (Robertson 1988, Meyer 1995). Nest sites in north Florida and

Georgia, however, were classified as needle-leaved evergreen (Pinus spp.) forests by the

88 GLC2000, and additionally described as pine fringe on lowland forest floodplains and hardwood

swamp forests (Robertson 1988, Meyer 1995).

The results of my range-wide analysis contrast with the stopover analysis in Chapter II.

The two analyses demonstrated an opposite pattern of habitat use in the Yucatan (selecting for

forests and avoiding agriculture). One explanation may be the substantial difference in the scale

of the remotely sensed data between the analyses. For example, at the large scale (1 km2) used in

this hemisphere analysis, what was classified as agriculture may appear to be a mosaic of both

forest and agriculture on the finer 30-m2 scale. Therefore, the finer scale may reveal that kites are

actually selecting for the patches of forest within an agriculture-dominated mosaic. Furthermore,

in addition to the scale difference of remotely sensed data, the size of the buffer differed (1500 m

for stopover; 5 km for hemisphere). Similarly to the pixel size above, this difference may reveal

that kites use an agricultural landscape within a forested mosaic within the large buffer, and when

the buffer is reduced to 1500 m, the size of the agriculture area is also reduced revealing kite use

in forested landscapes.

Another reason for the difference in habitat use between the analyses might be explained

by the size difference of the designated available areas in both analyses. In Chapter II the

available stopover area was delimited to the political boundaries of Belize and the Mexican State

of Quintana Roo, an area totaling 71,847 km2. In addition, Mexico and Belize were examined

separately with two different habitat schemes. The available area used in the hemisphere analysis

was a combination of this area, Yucatan State, most of Campeche, and part of Guatemala, totaling

an area of 177,995 km2 . The additional available area included in the hemisphere analysis

encompassed large tracts of forest representing the contiguous Meso-American Biological

Corridor comprised of the Maya Biosphere Reserve, Celestun Natural Park, Flamingo Mexicano

89 de Rio Largartos Natural Park and Calacmul Biosphere Reserve. This forested addition

consequently increased the available forested area, in which the kites did not spend much time.

Conservation. − The predominant forest type kites chose in the breeding season was

needle-leaved evergreen (Table 3.3), which includes industrial pine plantations on privately

owned lands. These forested land are usually under intensive management often including

clearcut practices, which could threaten kites. Habitat destruction and forest fragmentation have

had negative impacts on songbirds’ nest success due to an increase in predation (Temple and

Cary 1988, Robinson 1992) and nest parasitism by the brown-headed cowbird (Molothrus ater)

(Brittingham and Temple 1983). Fortunately for the Swallow-tailed Kite, there is currently a

program working with timber managers in Georgia and Florida to develop management

recommendations most beneficial to nesting kites (K. Meyer, pers. comm.).

The habitat selectivity of kites during stopover was minimal for the six habitat classes.

However, due to the abbreviated timeframe and the importance as a resting site after a long over-

water crossing, the stopover habitat kites associate with is vitally important for quick fat

deposition and rest. Forests in the Yucatan range from low deciduous, to moderately tall

semideciduous forests and dry tropical and tropical wet forests (Lynch 1989a). Even though the

Yucatan Peninsula was the most heavily forested location of the three examined in this study

(Table 3.2, Fig. 3.5), deforestation rates are currently the highest here as well (Myers 1980,

Buschbacher 1986). Migratory habitat has been largely overlooked as being a limiting factor for

birds (Moore et al. 1995, Hutto 2000). The brief, yet critical, habitat encounters birds

demonstrate along their migration can surely affect population trends (Sherry and Holmes 1996,

Yong et al. 1998).

Because this broad-scale analysis demonstrated that on winter ranges Swallow-tailed

Kites are only selective for forests, makes South American forests a prime target for preservation.

90 This is especially true for broadleaf evergreen forests, which was twice as common in kite areas

compared to the total available area (Table 3.7). This and many other forest types in South

America are vulnerable to deforestation in favor of grazing, firewood harvesting and the

construction of roads (Davis 1993, Stotz et al. 1996). Southeastern Paraguay, a region formerly

dominated by tall humid forest, has since been cleared in the last few decades for agriculture

(Hayes et al. 1990). A large portion of native habitat is now in some form of cultivation (the

greatest proportion of available habitat; 26%) in the designated winter area. Kites, however, are

avoiding these areas. The quality of winter habitat has been shown to affect the timing of spring

migration of birds and their physical conditions at departure, which influences their arrival dates

and physical condition on the breeding grounds (Rappole and McDonald 1994, Marra et al.

1998).

Analyses performed on remotely sensed data are constrained by the spatial and temporal

scales and spectral resolution of the data (Mack et al. 1997). For my analysis, however, 1-km

pixel size seemed appropriate in determining broad-scale habitat associations of Swallow-tailed

Kites. Furthermore, this scale is sufficient to account for the extensive range covered by a

Swallow-tailed Kite as it forages. Although kites in this study were choosy among the particular

finer-scale GLC2000 vegetation types within a season (e.g., broadleaved evergreen over

deciduous forests in South America), the analysis of plant structure and the six broad habitat

types were still useful for understanding range-wide habitat associations. The physical structure

of the plant communities is more important than the actual species composition to Swallow-tailed

Kites (Meyer 1995).

Many birds, including the Swallow-tailed Kites are most likely selecting foraging and

nesting sites based on landscape features that extend beyond the immediate location of the

telemetry fix (Meyer 1995, Retti and McLoughlin 1999). Likewise, any errors in the satellite-

91 telemetry locations were minimized by using a 5-km buffer around the locations (Retti and

McLoughlin 1999). This scale is also relevant to a management perspective, displaying the big

picture, and possibly identifying large preserves and continuous tracts of land to focus effort in

land protection.

Despite the results of this analysis, we must remember that the fate and limitations of

Swallow-tailed Kites depends on more than just the habitats it is found in. It is likely to be a

combination of several limiting factors that affect a population annually (Newton 1998). When

making conservation decisions, it is important to consider all seasons and locations birds face

throughout their annual cycle as well as their interaction (Webster et al. 2002).

Chapter IV

The Blood Parasites and Ectoparasites of Swallow-tailed Kites

in Florida and Georgia

Introduction

Parasites, both internal and external, are common in birds (Newton 1998, Blanco et al.

2001). For example, haematozoan parasites have been found in 2500 of 4000 bird species

examined as of 1992 (Bennett et al. 1992), and over 2500 species of mites are known from birds

worldwide (Proctor and Owens 2000). The effects of these parasites range from minor

discomforts such as dermatitis (Blanco et al. 2001, Proctor 2003) to debilitating or even fatal

parasite loads (Newton 1998). In some cases, species classified as ectoparasites, such as feather

mites (Acari: Astigmata), may be commensal or even beneficial to birds by removing old oils,

pathogenic microorganisms, and feather-degrading bacteria (Blanco et al. 2001, Proctor 2003).

Given the diversity of avian parasites and their range of effects, there is increasing

interest in their evolutionary and ecological impacts on birds. For instance, the Hamilton-Zuk

hypothesis inspired a host of studies on the coevolution of birds and their parasites (Hamilton and

Zuk 1982, Møller 1990, Wiehn et al. 1997). This hypothesis states that the secondary sex

characteristics of males are reliable indicators of heritable resistance to parasites and thus an

adaptive cue for female mate choice (Hamilton and Zuk 1982). Ecological studies demonstrate

that parasites can also impact avian reproductive success (Korpimaki et al. 1993, Richner et al.

1993, Saino et al. 2002), and in combination with other limiting factors (e.g., food shortages,

environmental condition and predation) can affect adult survival (review in Newton 1998). The

93 ecological effects of parasites may be heightened when the host is undergoing intense energetic

demands such as egg laying (Korpimaki et al. 1993), early development (Merino et al. 1996,

Heeb et al. 2000, Sol et al. 2003), or migration (Piersma 1997). Not only does migration

represent a significant energy demand, migratory birds are also exposed to diverse communities

of parasites along their migratory route. As a consequence, migrants may have larger immune

defense organs than resident birds (Møller and Erritzoe 1998).

Although these and other studies demonstrate serious evolutionary and ecological effects

of parasites, the specific role of parasites in birds is a relatively unknown subject. An obvious

prerequisite to understanding bird-parasite interactions is to identify the parasite fauna associated

with each host species. The parasite fauna of some birds are better known than others because of

the relative ease in obtaining the birds for examination (e.g., domestic fowl and other captive

birds; Loye and Zuk 1991). Rare or difficult-to-capture birds (such as raptors) are inadequately

surveyed for parasites (Powers et al. 1994, Philips 2000).

One such raptor is the Swallow-tailed Kite (Elanoides forficatus), a migratory bird that

breeds in the southeastern United States and winters in South America. Because Swallow-tailed

Kites are uncommon and hard to catch, their parasites are poorly studied. Parasite records from

Swallow-tailed Kites are limited to a brief documentation of a few tremetodes, nematodes, mites,

and lice removed from two dead nestlings (Forrester and Spalding 2003), a type host report of a

chewing louse (Clay 1958a, 1958b), and a description of two additional chewing lice by Kellogg

(1896). In addition to limited documentation, there are no parasite collection records from the

state of Georgia and only a few kites have been examined in Florida. Furthermore, there are no

blood smear records from Swallow-tailed Kites describing their haemoparasites.

The objective of my study was to provide the first systematic examination of the

ectoparasites and blood parasites of Swallow-tailed Kites. Parasites may play a direct or indirect

94 role in the life cycle of Swallow-tailed Kites, a declining species with an energetically demanding

migration through a range of temperate and tropical ecosystems. My research seeks to identify

some of the parasite species associated with Swallow-tailed Kites in order to provide a basis for

further investigation of kite-parasite interactions. In this study, I determined the prevalence and

diversity of ectoparasites and blood parasites of Swallow-tailed Kites in two study populations

(Levy Co., Florida, and southeastern Georgia). I also compared differences in the parasite

diversity and abundance between states (Georgia versus Florida), age classes (nestlings versus

adults), and sexes (males versus females).

Methods

From May-July 2002 and 2003, I assisted the Avian Research and Conservation Institute

and the Georgia Department of Natural Resources in capturing adult and nestling Swallow-tailed

Kites in order to outfit them with radio-transmitters for demographic and long-distance migration

studies. Adult kites were lured into a large (12 m x 8 m) mist-nets using a live Great Horned Owl

(Bubo virginianus) to elicit mobbing by kites in defense of their young. Nestlings 28-33 days old

were captured in the nest.

On Plum Creek Timber Co. property (Gulf Hammock) in Levy Co., Florida, we captured

nine adults in 2002 and one nestling in 2003. In Georgia, trapping locations were dispersed

throughout seven counties (Bryan, Liberty, Long, Wayne, Brantley, Glynn, and Camden) in the

southeastern coastal plain (Fig 4.1, Table 4.1). In 2002, 4 adults and 12 nestlings were captured.

In 2003, 4 adults and 8 nestlings were captured in Georgia. All captured kites (n = 38) were

surveyed for parasites.

Blood parasites. − I drew a 1-cc sample of blood from each kite with a 28-guage needle

from the brachial vein for DNA sex-determination. I used two drops of this blood to make blood

95

Figure 4.1. Collection locations in Georgia and Florida for blood parasites and ectoparasites from Swallow-tailed Kites in 2002 and 2003.

96 Table 4.1. Trapping location, age, and sex of 38 Swallow-tailed Kites sampled for blood parasites and ectoparasites in 2002 and 2003.

Bird ID Age Sex State County Capture date

1702 Adult F FL Levy May-02 1802 Adult F FL Levy May-02 2102 Adult F FL Levy May-02 2202 Adult F FL Levy May-02 2502 Adult F FL Levy Jun-02 1902 Adult M FL Levy May-02 2002 Adult M FL Levy May-02 2302 Adult M FL Levy May-02 2402 Adult M FL Levy May-02 302 Nestling M FL Levy May-03 313 Adult F GA Brantley Jun-03 802 Adult F GA Brantley Jun-02 316 Nestling F GA Brantley Jun-03 317 Nestling F GA Brantley Jun-03

1302 Nestling F GA Brantley Jun-02 1202 Nestling F GA Brantley Jun-02 602 Nestling M GA Brantley Jun-02

1102 Nestling M GA Bryan Jun-02 1502 Adult F GA Camden Jun-02 312 Adult M GA Camden Jun-03

1402 Adult M GA Camden Jun-02 304 Nestling M GA Camden Jun-03 305 Nestling M GA Camden Jun-03 307 Nestling M GA Camden Jun-03

1602 Nestling M GA Camden Jul-02 311 Adult M GA Glynn Jun-03 306 Nestling F GA Glynn Jun-03 202 Nestling F GA Liberty Jun-02 102 Nestling M GA Liberty Jun-02 314 Adult F GA Long Jun-03 502 Adult F GA Long Jun-02

1002 Nestling F GA Long Jun-02 309* Nestling F GA Long Jun-03 315 Nestling M GA Long Jun-03 902 Nestling M GA Long Jun-02

310* Nestling M GA Long Jun-03 302 Nestling M GA Wayne Jun-02 402 Nestling M GA Wayne Jun-02

97 smears (following Pung et al. 2000) on microscope slides for blood parasite examination. I

recorded the date, bird ID number, age (nestling or adult), and state trapped on each slide. Air-

dried slides were immediately fixed in 75% methanol for 5 min in the field and stored in a slide

box at room temperature. Two months later, I stained one slide from each bird with Wright’s

stain for 10 min, rinsed with distilled water, and then counter stained with Giemsa stain (Sigma

Chemical Co., St. Louis, Missouri) (Pung et al. 2000).

I initially scanned the entire slide at 40x under a bright field microscope for large

parasites such as trypanosomes and microfilarial nematodes in the plasma. This was followed by

a 10-min scan at 100x and a 10-min scan with the oil immersion lens at 1000x to observe any

hematozoa within the erythrocytes. For each slide, I tallied the number of blood parasites and

identified each to the lowest possible taxon.

Ectoparasites. − After drawing the blood sample, I applied approximately 1

tablespoon/bird of Zema Z3 flea and tick powder for dogs (St. Jon Laboratories Inc., Harbor City,

California) containing pyrethrin, onto the feathers of five body regions (one wing, back, rump,

around keel, and underside of tail) and worked it into each region for 5 min to dislodge

ectoparasites (Clayton and Drown 2001). I held the kite over a large (30 cm x 45 cm) collecting

surface fashioned from sturdy, black paper, while ruffling the feathers by hand to release the

dying parasites. After ruffling, I examined the bird closely and used a forceps to remove

additional parasites that were not removed with the pyrethrin dust. All specimens were collected

from the construction paper with a forceps and preserved in a vial of 70% ethanol, marked with

the same identifiers as their corresponding blood slides, and stored at room temperature.

I identified ectoparasites to the lowest taxon possible by clearing and mounting about ten

specimens of each ectoparasite species on a microscope slide and examining under a dissecting

microscope. This also facilitated identification of the sexes and life stages (e.g., nymph or adult)

98 present. Using a clearing method similar to that reported in Kim et al. (1986), I pricked each

specimen in the abdomen, placed it in KOH for at least 24 hr, rinsed it with distilled water, and

gradually transferred it to absolute ethyl alcohol in 10-min increments from 50%, 70%, 80%,

95%, and then 100%. Specimens were then placed in xylene for 5 min and mounted one or two

per slide, in Canada balsam mounting medium.

I tallied the number of individuals, as well as their sex and life stage (when known), for

each parasite species on each kite. I then calculated the prevalence (% of birds infested) and

intensity (mean number of specimens/bird) of each ectoparasite species (sexes and life stages

combined) to determine if there were differences in parasite loads between adult kites versus

nestlings, males versus females, or Florida versus Georgia. Analyses were performed using

Mann-Whitney U-tests with JMP statistical software (SAS Institute, Inc.).

Voucher ectoparasite specimens were deposited in the Institute of Arthropology and

Parasitology at Georgia Southern University under accession numbers L3145-L3148 and L3286.

An additional voucher feather mite specimen was deposited in the Zoological Institute of the

Russian Academy of Sciences, St. Petersburg (accession number: ZISP-4334).

Results

Blood parasites. − I examined blood smears from 38 Swallow-tailed Kites. Twenty-

eight kites were from Georgia and ten from Florida (Table 4.1). There were 17 adults, and 21

nestlings, made up of 20 males and 18 females. I found no haemosporidian parasites, and only 3

birds (7.9%) were infected with either a trypanosome or a microfilarial nematode. The

trypanosome was from an adult female from Florida. One microfilarial nematode was found in

the blood of a nestling female, while the other was from an adult male, both from Georgia.

Ecotparasites. − All but two nestlings (Bird ID 309 and 310; Table 4.1) from the above

sample were examined for ectoparasites (n = 36). I found a total of 461 ectoparasite specimens

99 representing six species on these Swallow-tailed Kites. An average of 21.5 ectoparasites (range

0-136) was found on individual kites (Table 4.2).

Three of the ectoparasite species infesting kites were Mallophagan chewing lice

(Cuculiphilus decoratus, Colpocephalum osborni, and Degeeriella guimaraesi). Adult males,

adult females, and nymphs of all three of these species occurred on Swallow-tailed Kites (Table

4.2). The sex ratio of C. osborni was female biased (X2 = 5.56, df = 1, P < 0.05).

I also found female and nymphs of the blood-feeding mite Ornithonyssus bursa, a

mesostigmatid (gamasid) mite belonging to the family Macronyssidae. The final two species

removed from Swallow-tailed Kites were new species of feather mites belonging to the family

Gabuciniidae; one of these may represent a new genus (Sergei Mironov Russian Academy of

Sciences, St. Petersburg and Dr. Heather Proctor, University of Alberta, pers. comm.).

In general, male kites had higher ectoparasite loads than females (mean intensity), and

birds from Georgia had more ectoparasites than those from Florida (Table 4.3). However, the

only statistically significant difference was for kites from Georgia to have a higher intensity of

Colpocephalum osborni than Florida (Table 4.3). This statistical difference did not persist if I

applied a correction for multiple tests.

Discussion

My study represents the first thorough survey of blood parasites and ectoparasites of

Swallow-tailed Kites. In addition, this is the first time any parasite examination has been

conducted on Swallow-tailed Kites in Georgia. The trypanosome and microfilaria specimens

were the first records of any blood parasites found in Swallow-tailed Kites. In addition, my

survey probably revealed two new species of feather mites.

Blood parasites. − Blood parasite diversity and prevalence was low in Swallow-tailed

Kites; I found only one trypanosome or microfilaria specimen per slide for 3 of 38 Swallow-

100 Table 4.2. Prevalence and intensity of ectoparasites from 37 adult and nestling Swallow-tailed Kites examined in Florida and Georgia in 2002 and 2003. Total

Ectoparasites Prevalence

(%) Mean intensity

± SE Intensity

range Male Female Nymph Mallophagan chewing lice Cuculiphilus decoratus 30 0.86 ± 0.33 1 - 11 15 13 4 Colpocephalum osborni 57 6.41 ± 2.16 1 - 54 76 108 53 Degeeriella guimaraesi 51 1.73 ± 0.40 1 - 8 27 27 10 Blood-feeding mite Ornithonyssus bursa 14 0.49 ± 0.38 1 - 14 18a Acari feather mites New Aetacarus species 32 2.97 ± 1.14 1 - 28 110a New gabuciniid genus 3 0.03 ± 0.03 1 1 Total 84 21.5 ± 5.03 1 - 136 aTotal specimens (unknown sex or life stage)

101 Table 4.3. Comparison of ectoparasite intensity/bird performed on five species of ectoparasites and total ectoparasite loads of 37 Swallow-tailed Kites sampled in 2002 and 2003. P values based on Mann-Whitney U-tests.

Cuculiphilus decoratus Colpocephalum osborni Degeeriella guimaraesi Category Mean SE Z P Mean SE Z P Mean SE Z P Male 1.3 0.58 7.4 2.98 2.0 0.51 Female 0.4 0.21 1.49 0.14 5.3 3.21 0.59 0.56 1.4 0.63 1.48 0.14

Adult 0.7 0.27 6.5 3.43 1.8 0.54 Nestling 1.1 0.58 0.36 0.72 6.4 2.81 0.18 0.86 1.7 0.58 0.62 0.54

FL 0.3 0.21 0.6 0.40 2.2 0.73 GA 1.1 0.45 0.91 0.36 8.6 2.86 2.30 0.02 1.6 0.48 1.20 0.23

Total 0.9 0.33 6.4 2.16 1.7 0.40 Ornithonyssus bursa Aetacarus sp. Total ectoparasites Category Mean SE Z P Mean SE Z P Mean SE Z P Male 0.9 0.70 2.7 1.53 24.9 7.44 Female 0.1 0.06 1.23 0.22 3.3 1.77 0.09 0.93 17.5 6.68 0.76 0.45

Adult 12.0 0.08 3.8 1.70 21.8 6.92 Nestling 0.8 0.60 0.31 0.76 2.3 1.55 1.67 0.10 21.2 7.38 1.01 0.31

FL 0.1 0.70 2.3 1.38 8.6 2.37 GA 0.6 0.52 0.38 0.71 3.2 1.49 0.12 0.90 26.2 6.64 1.12 0.27

Total 0.5 0.38 3.0 1.14 21.5 5.03

102 tailed Kites (7.9%). This suggests that haematozoa are rare in Swallow-tailed Kites. However,

trypanosome parasitemias may be hidden in the bone marrow rather than in the peripheral blood

(Merino et al. 1996). Likewise, mircofilaria are only periodically released into circulating blood

from filarial nematodes living in host tissue (Atkinson and Van Ripper 1991), thus sometimes

making detection difficult. Larger samples or more detailed studies would be needed to eliminate

these possibilities.

Nevertheless, other blood parasite studies on birds in the southeastern U.S. have found

low infestation rates. One survey of birds in southwestern Georgia found 48 of 97 species to be

free of blood parasites (Love et al. 1953), and another by Pung et al. (2000) only found six of 67

Red-cockaded Woodpeckers (Picoides borealis) to be infected with blood parasites in

southeastern Georgia. Conversely, Telford et al. (1997) found all tested raptor species in Florida

and southern Georgia to have plasmodium blood parasites, although the prevalence of infection

ranged from 4.2% to 33.3%. Likewise, in another Florida raptor survey, 11 of 15 species tested

had blood parasites (Forrester et al. 1994).

The absence of hematosporidian blood parasites in Swallow-tailed Kites is noteworthy in

itself. The lifestyle and foraging habits of Swallow-tailed Kites probably reduces their

susceptibility to some vectors of blood parasites (e.g. mosquitoes, biting flies). Swallow-tailed

Kites spend most of their day on the wing as they forage for aerial insects and vertebrates high in

the tree canopy (Meyer 1995, Meyer et al. 2004), reducing their contact with ground vegetation

that may harbor some vectors. However, it is somewhat surprising that especially nestling kites

did not show some sign of hematosporidian blood parasites because biting flies and mosquitoes

are more prevalent in forested areas (Tella et al. 1999) and the tree canopy (Garvin and Remsen

1997) where Swallow-tailed Kite nests are located.

103

A lack of vectors has been implicated previously as an explanation for the absence of

blood parasites in birds (Figuerola et al. 1996, Tella et al. 1996, Blanco et al. 1998, Tella et al.

1999, Martinez-Abrain and Urios 2002). Most studies relate reduced vector exposure to the

nesting habitat the birds are found in, whether nesting in arid and open lands (Tella et al. 1996),

small remote islands (Little and Earle 1994), or marine environments (Martinez-Abrain and Urios

2002).

Ectoparasites. − I found a total of six ectoparasite species on Swallow-tailed Kites. This

number is also low compared to the diversity of ectoparasites found on some birds, especially

ground-dwellers. A single bird species may host up to 25 mite species alone (Gaud and Atyeo

1996), and 21 species of ectoparasites were found on Northern Bobwhite (Doster et al. 1980) in

the southeastern U.S.

The three Mallophagan lice and the blood-sucking mite Ornithonyssus bursa that I found

in my survey of Swallow-tailed Kites were also discovered on two dead nestlings investigated in

Florida (Forrester and Spalding 2003). Two of the chewing lice species (Colpocephalum osborni

and Cuculiphilus decoratus) were first found and described on White-tailed Kites (Elanus

leucurus) in California (Kellogg 1896) and since have been reported on Swallow-tailed Kites

(Price and Beer 1963, Emerson 1972, Forrester and Spalding 2003). Because Mallophagan lice

(suborder Amblycera) often prefer different microhabitat locations on a bird, one host may be

parasitized by many species at a time (Romoser and Stoffolano 1998) as seen in this study. These

lice feed on various organic fragments of feathers and skin, and epidermal secretions (Romoser

and Stoffolano 1998). Unlike Forrester and Spalding (2003), I did not detect any mites from the

genus Macrocheles. This is not unusual, since these mites are usually associated with soil (non-

phoretic) or bird dung (phoretic) rather than the birds themselves (Walter and Proctor 1999).

104

The species of blood-sucking mite that I found on Swallow-tailed Kites (Ornithonyssus

bursa) is a ubiquitous parasite found on raptors (Philips 2000) and other birds worldwide (Proctor

and Owens 2000). It is the least host-specific of all the ectoparasites I found, but it is known to

have a significant impact on hosts. Female Barn Swallows (Hirudina rustica) choose mates with

fewer O. bursa mites, and host resistance to these mites appears to be heritable (Møller 1990).

Other members of the genus Ornithonyssus have caused a reduction in fecundity (Kettle 1995),

virility (Walter and Proctor 1999), and brood sizes in birds (Saino et al. 2002), as well as slowed

nestling development (Saino et al. 2002). Besides these direct effects on host species, this blood-

feeding mite is also a vector in disease transmission (Sonenshine 1993, Kettle 1995).

I discovered two potentially new species of feather mites on Swallow-tailed Kites. I am

collaborating with Dr. Heather Proctor at the University of Alberta, Canada in the description of

these specimens. Both mites are in the family Gabuciniidae, which infest raptors exclusively

(Philips 2000). One mite may be a member of the genus Aetacarus, while the other may

represent a new genus. In the survey of two dead nestling kites (Forrester and Spalding 2003), a

mite from the genus Aetacarus was also discovered, which potentially could be the same species

as one of the new feather mites from this study. These types of feather mites are usually host

specific (Walter and Proctor 1999). Thus, the Swallow-tailed Kite may be the only bird species

in which they are found (implying that these species may share threatened status with the kites

themselves). Aetacarus feather mites live largely on the primaries and their upper coverts on the

wings of raptors (Philips 2000). Here they feed on feather fragments, lipid secretions, skin

debris, fungi, bacteria, and algae; they are usually not considered to cause harm to their hosts

(Philips 2000, Proctor and Owens 2000, Blanco et al. 2001, Proctor 2003). Philips (2000) found

that mites on raptors rarely cause harm unless they are very abundant.

105

All the ectoparasites found in my study are passed from host to host by direct contact

(Proctor and Owens 2000). This can be done vertically from kite to kite, parent to offspring

(Proctor 2003), or horizontally between host species (Gaud and Atyeo 1996). Some mites get

transported between hosts by hippoboscid flies (Gaud and Atyeo 1996, Jovani et al. 2001).

Transmission in Swallow-tailed Kites is probability facilitated by the fact that they are social

raptors that forage together on swarms of flying insects and rest at night in communal roosts of up

to 3000 individuals (Meyer 1998). Furthermore, on their wintering grounds Swallow-tailed Kites

congregate with other migrant Swallow-tailed Kites, breeding Swallow-tailed Kites (E. f. yetapa),

wintering flocks of Mississippi Kites (Ictinia mississippiensis) and wintering and breeding

Plumbeous Kites (Ictinia plumbea) (K. Meyer, pers. obs.).

Parasites often affect sex and age classes differentially. Breeding female Tengmalm’s

Owls (Aegolius funereus) were found to have higher blood parasite loads than their mates,

consequently affecting clutch size (Korpimaki et al. 1993). In a literature review on 35 sex-

biased parasitism studies, McCurdy et al. (1998) also found that breeding female birds had higher

blood parasite infections than males. Juveniles may be more severely affected by parasites than

adults because they have a less efficient immune response (Merino et al. 1996, Sol et al. 2003), or

because of an increase in uropygial gland oil which attracts some ectoparasites as a food source

(Dowling et al. 2001). In addition, nestling and adult birds have different behaviors, which may

expose them to different parasites (vector exposure hypothesis) (Figuerola et al. 1996, Blanco et

al. 1998, Martinez-Abrain and Urios 2002). However, I found no significant difference between

sexes or age classes.

In summary, my survey of blood parasites and ectoparasites shows that Swallow-tailed

Kites are infected by a low parasite diversity yet taxonomically distinct. This survey also

revealed at least one mite known to be harmful to host species (Ornithonyssus bursa). Further

106 research should focus on the potential problems O. bursa might cause Swallow-tailed Kites.

Additionally, it would be useful to compare parasite surveys from kites in other populations in the

U.S. and throughout Central and South America.

Chapter V

Summary

The Swallow-tailed Kite is one of the most poorly studied raptors in the United States.

Because of a dramatic and ongoing population decline (Cely 1979, Meyer 1995), it rates as a top

priority species for conservation action in the U.S. However, action is hampered by the fact that

little is known about its basic ecology. Of the studies done on Swallow-tailed Kites, most have

been restricted to their breeding grounds despite the fact that they spend more than 60% of the

year outside of the U.S., and travel at least 15,000 km over two continents. There is a pressing

need for research on the factors that may be contributing to the rarity of the Swallow-tailed Kite,

some of which may be related to the diversity of locations encountered throughout their annual

cycle.

Given this need, my research addressed four important issues concerning the annual cycle

of Swallow-tailed Kites. First, I predicted that Cuba and/or the Yucatan Peninsula would be

important stopover sites for Swallow-tailed Kites because of their location on (Cuba) or just after

(Yucatan) a long, water crossing. Contrary to the predictions, kites passed through Cuba quickly

with no evidence of slower travel or wandering movements. However, as predicted, the Yucatan

Peninsula did appear to be a stopover site for southbound migrating kites. Once on land the kites

slowed down and noticeably deviated from a southerly course (Figs. 2.4–2.6 and 2.8). The

satellite data showed that the kites on the peninsula were meandering in all directions (Fig. 2.8

Appendix A), most likely in search of foraging sites to fatten up for the rest of their journey.

Second, given that there was evidence of stopover on the Yucatan Peninsula, I predicted

that Swallow-tailed Kites would be selective in their habitat choice there. I did find this to be

108 true. Kites avoided disturbed areas and areas without vegetation in favor of lowland broadleaf

forests (Tables 2.8). Furthermore, kites were found in heterogeneous patches of vegetation more

than expected at random, which supports other studies which associate kites with forest edges due

to their foraging strategy (Robertson 1988, Meyer 1995, Meyer et al. 2004).

Third, I examined hemisphere-wide Swallow-tailed Kite habitat associations. Forested

habitat was the most common habitat type in areas used by kites during all seasons (Table 3.3).

However, there were subtle and interesting differences in habitat use among seasons. The habitat

compositions for nest sites split nests into two groups, those dominated by forests, and those

dominated by wetlands. Additionally, wetlands only appeared important during breeding. At this

scale, agricultural landscapes appeared to be important to kites during stopover on the Yucatan

Peninsula. Furthermore, on their winter range, Swallow-tailed Kites avoided most of the broad

habitat classifications, only to select lands dominated by forests. Kites were most selective in

overall habitat choice during the nesting season and least selective on the Yucatan (Table 3.3).

Finally, I surveyed blood parasites and ectoparasites from Swallow-tailed Kites in

Georgia and Florida, and found a relatively low diversity and low infestation. Of the six

ectoparasite species I found on kites, one blood-sucking mite (Ornithonyssus bursa) has caused

problems to other bird hosts, and two are new species of feather mites, of which one could be a

new genus. As a migratory bird, the Swallow-tailed Kite is exposed to parasites inhabiting all

ecosystems along the migration route. My research is the first thorough parasite survey

performed on Swallow-tailed Kites. Never before have any blood parasites been documented for

this species. Furthermore, there are no collection records for parasites found on Swallow-tailed

Kites in Georgia.

My results contribute to our understanding of the movements and habitat use of Swallow-

tailed Kites across their annual cycle. However, my work also points to areas where more study

109 is needed. For one, we need to understand the differences between juvenile kites and adults in

their migratory route and habitat use if any. Previous satellite studies on raptors of various ages

have shown different routes and migration rates between adults and juvenile birds (Kjellen et al.

2001, Meyberg et al. 2001). It is important in terms of conservation to identify all the areas used

by kites of different sexes and ages, so the proper protection to those locations can be taken into

account (Hutto 1998).

My analysis ascertained habitat associations of Swallow-tailed Kites based on

measurements of landscape features on a broad, hemisphere-wide scale. However, analyzing

habitat use and availability, as well as kite behavior, should be quantified on smaller scales using

greater precision in the remotely-sensed data. By acquiring smaller-scale (e.g., 30-m pixel size)

remotely-sensed data within the countries along the entire migratory pathway, the specific

regional plant communities can be identified for additional importance to Swallow-tailed Kites.

Additional habitat analyses should be conducted on the other possible stopover sites and

constriction points where all U.S. kites must pass through. Specifically, the migration route

shows a concentration on the narrow isthmus of Panama and along the Andes mountains in

Columbia, plus a rate reduction in northern Bolivia and western Brazil (Fig 2.4-2.6). Ideally, the

entire narrow migration route of Swallow-tailed Kites should be mapped and examined for

habitat associations to recognize the threats kites may face throughout their migration.

Some parasites are known to cause developmental, reproductive, and behavioral

problems in their hosts. It is important now to assess the virulence of the parasite species I

discovered on Swallow-tailed Kites. The species that comes to mind as potentially threatening is

the blood-sucking mite O. bursa, which can impact host fitness and mate selection in other birds

(Møller 1990, and see review in Proctor and Owens 2000), as well as transmit blood-borne

diseases (Kettle 1995, Sonenshine 1993).

110 In conclusion, the findings of my research has answered questions regarding the evidence

of stopover on the Yucatan Peninsula, the broad habitat associations of kites throughout their

annual cycle, and blood parasite and ectoparasite prevalence and intensity of Swallow-tailed

Kites. Because kites are rare and hard to capture, basic research on their natural history is

limited. This study has increased our knowledge on many aspects of its ecology, information that

may bring us closer to quantifying limiting factors that affect the Swallow-tailed Kite throughout

its annual cycle.

111

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122

APPENDICES

123 Appendix A. The following pages (124-129) show the individual southbound migration routes of 25 Swallow-tailed Kites tracked by satellite from the western shore of Cuba through the Yucatan Peninsula that migrated in years 2000 to 2003.

124

125

125

126

127

128

129

129

Appendix B. Southbound migration of Swallow-tailed Kite #16083 tracked by satellites in 2002 and 2003.

130

131

Appendix C. The southbound migration of Swallow-tailed Kite #16031 from Florida through Nicaragua tracked by satellites in 2002.