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Ornithological Monographs No. 50
Avian Community, Climate, and Sea-Level Changes in the
Plio-Pleistocene of the Florida Peninsula
Steven D. Emslie
AVIAN COMMUNITY, CLIMATE, AND SEA-LEVEL CHANGES IN THE
PLIO-PLEISTOCENE OF THE
JOHN M. HAGAN
Mahomet Center for Conservation Sciences
14 Maine St., Suite 404 Brunswick, Maine 04011
Ornithological Monographs, published by the American Ornithologists' Union, has been established for major papers too long for inclusion in the Union's journal, The Auk. Publication has been made possible through the generosity of the late Mrs. Carll Tucker and the Marcia Brady Tucker Foundation, Inc.
Copies of Ornithological Monographs may be ordered from Max C. Thompson, Assistant to the Treasurer, Department of Biology, Southwestern College, 100 College St., Winfield, Kansas 67156. Communications may also be routed through the AOU's permanent address: Division of Ornithology, National Museum of Natural History, Washington, D.C. 20560.
Author of this issue, Steven D. Emslie.
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Library of Congress Catalogue Card Number 98-072819
Printed by Allen Press, Inc., Lawrence, Kansas 66044
Issued September 3, 1998
Ornithological Monographs, No. 50 iii + 113 pp.
Copyright ¸ by the American Ornithologists' Union, 1998
AVIAN COMMUNITY, CLIMATE, AND SEA-LEVEL CHANGES IN THE
PLIO-PLEISTOCENE OF THE
STEVEN D. EMSLIE
Department of Biological Sciences University of North Carolina
601 S. College Road Wilmington, North Carolina 28403 USA
ORNITHOLOGICAL MONOGRAPHS NO. 50
THE AMERICAN ORNITHOLOGISTS' UNION
Ornithological Monographs Volume (1998), pp. 1-113
AVIAN COMMUNITY, CLIMATE, AND SEA-LEVEL CHANGES IN THE PLIO-PLEISTOCENE
OF THE FLORIDA PENINSULA
STEVEN D. EMSLIE 1 Department of Biological Sciences, University of North Carolina, 601 S. College Road,
Wilmington, North Carolina, USA
ABSTRACT.---Eleven previously unidentified fossil avifaunas from Pliocene and Pleistocene localities in the Florida peninsula are presented, within which are included the description of a new species of anhinga (Anhinga beckeri), woodcock (Scolopax hutchensi), and pygmy-owl (Glaucidium explorator), and a new genus and species of condor (Aizenogyps toomeyae). The paleospecies Milvago readei, Dorypaltus prosphatus, and Protocitta dixi are considered to be synonymous with the living taxa Milvago chimachima, Vanellus chilensis, and Pica pica, respec- tively. These 11 avifaunas supplement the existing record of fossil birds from Florida that collectively provide a unique chronology of ofiginations and extinc- tions of 239 extinct and extant taxa during a climatically dynamic period that began approximately 2.5 million years ago (Ma). Topographic and bathymetfic maps of the peninsula are used with Geographic Information Systems software to model and correlate sea-level changes with the location and age of major fossil sites, the avian chronology, and presumed primary habitat of each represented taxon. These analyses indicate range expansions of Neotropical, western North American, and continental forest birds into the Florida peninsula during glacial stages, and the isolation, extirpation, or extinction of many of these taxa during interglacial stages. The relatively rapid climatic cycles of the Plio-Pleistocene, combined with the low topography of the peninsula, caused significant loss of wetland habitat during interglacial marine transgressions, especially in southern Florida. This habitat reduction probably accounted for extinctions of many wet- land birds, especially those with relatively small body-size, in the late Pliocene. Additional extinctions recorded in the early Pleistocene resulted in a gradual loss of species richness in these communities by the end of the Pleistocene, when modern wetlands were established. Climatic events in the Pleistocene influenced
terrestrial communities with the periodic formation and fragmentation of the Gulf Coast corridor, a mosaic of dry, thorn-scrub, savannah, wetlands, and hammocks, that united Neotropical regions to the south with western North America and the Florida peninsula. This corridor developed with the emergence of the shallow continental shelf in the Gulf of Mexico during glacial stages, which in some cases more than doubled the land area of the peninsula and allowed numerous species of mammals, birds, reptiles, and plants to extend their ranges into Florida. Frag- mentation of this corridor during interglacial stages caused loss of species rich- ness, probably from loss of habitat heterogeneity in the peninsula. Unlike wetland communities, modern terrestrial communities did not develop until the early Ho- locene, after the last fragmentation of the corridor and extinction event at 0.01 Ma. Fossil passefine remains suggest that North American continental migration patterns began developing in the peninsula in the late Pliocene, and were fully established by the late Pleistocene, but Neotropical migration patterns may not have developed until the early Holocene. The chronology presented here provides a model of avian biogeography and community development in the Florida pen- insula during the ice ages that can be tested with future paleontological research.
E-mail: [email protected]
2 ORNITHOLOGICAL MONOGRAPHS NO. 50
Those who are unfamiliar with the geology of Florida are often surprised to learn of the excellent fossil record of vertebrates known from this state. This
record includes the most complete chronology of extinct and extant birds in the Neogene of North America. The avian record beginning 2.5 million years ago (Ma), from the initiation of the ice ages in the late Pliocene to the end of the last major glaciafion (the Wisconsinan) in the late Pleistocene at 0.01 Ma, is partic- ularly well known from dozens of localities that span this period and from the extensive research that has been completed on fossil birds in Florida by Dr. Pierce Brodkorb and his students since 1952 (see Campbell 1992). This monograph is a culmination of more than 14 years of research by the author on Plio-Pleistocene birds in the Florida peninsula. Here, I present the systematic paleontology of avifaunas recovered from four new and seven previously described fossil localities that includes the description of one new genus and four new species, and the identification of 23 extant and three extinct species previously unreported as fos- sils from Florida.
I use this extensive addition to Florida's fossil record with data from numerous
previously published avifaunas, with certain modifications, to develop a 2.5 mil- lion-year chronology of extant and extinct birds in the peninsula. I compare this avian chronology with the glacial and interglacial stages that caused sea-level changes during the Plio-Pleistocene to discern patterns in avian originations and extinctions during this climatically dynamic period. Geographic Information Sys- tems (GIS) software (Idrisi 1.01, Clark Univ., Worcester, MA) is employed to model sea-level changes in the peninsula during five time periods from 2.5 to 0.01 Ma. Patterns in these originations and extinctions, based on probable habitats occupied by these birds, are inferred from these comparisons to develop a model of avian historical biogeography and community development during the Plio- Pleistocene. My primary hypothesis here is that, because of its low topography and geography, the Florida peninsula was subject to relatively frequent and rapid changes in land area during the ice ages when even minor sea-level changes (1 m or less) impacted this region. As I will demonstrate below, these changes over the past 2.5 Ma had a significant influence on the composition of avian com- munities in the peninsula where modem communities developed only recently. This model can be tested and refined with future additions to the fossil record of
Florida. The model also may prove beneficial for estimating future changes to avian communities in the Florida peninsula in conjunction with other climate models on this region (e.g., Box et al. 1993).
Systematic analyses and comparisons of fossil material were completed at the Florida Museum of Natural History, Gainesville (FLMNH), the U.S. National Museum of Natural History, Washington, D.C. (USNM), the University of Mich- igan Museums of Paleontology (UMMP) and Zoology (UMMZ), Ann Arbor, the American Museum of Natural History, New York (AMNH), and the Natural His- tory Museum of Los Angeles County (LACM). Terminology follows that of How- ard (1929). Most fossil specimens reported here are catalogued with University of Florida (UF) numbers, or with UF/PB numbers for specimens originally in the collection of Pierce Brodkorb. All measurements were taken with digital calipers, rounded to the nearest 0.1 min.
PLIO-PLEISTOCENE BIRDS OF FLORIDA 3
Excavations were conducted at two fossil localities (Haile 7C and Inglis 1C, see below) to obtain additional avian fossils, and to collect paleomagnetic and pollen samples for chronological and paleoe