Avian specializationsAvian specializations

Chapter 17

Mesozoic bird radiationsMesozoic bird radiations

• Enantiornithes – metatarsals are fusedEnantiornithes  metatarsals are fused differently than modern birds, also retained teethteeth– Dominant in the cretaceous

• Ornithurines appeared later in the• Ornithurines – appeared later in the cretaceous, variety of ecological types

Modern birdsModern birds

• Neornithes – late cretaceousNeornithes  late cretaceous– about 9672 extant species

Split into two major groups– Split into two major groups• Palaeognathae (Ratites)

• NeognathaeNeognathae

FeathersFeathers

• Calamus – anchorsCalamus  anchors feather to skin

• Rachis• Rachis

• Barbs

FeathersFeathers 

• 5 types of feathers5 types of feathers– Contour feathers

• Remiges – wing feathers

• Retrices – tail feathers

– Semiplumes – large rachis with plumulaceous vanes

– Down – entirely plumulaceous and rachis is shorter than the longest barb or absent

– Bristles – stiff rachis and barbs only at the ybase or absent

– Filoplumes – fine hairlike feather with few short barbs at the tip, used for sensoryp, y

SkeletonSkeleton

• Pneumatic bonesPneumatic bones

f i• Bone fusions – Synsacrum

– Pygostyle

– Furcula

– Tarsometatarsus

– Tibiotarsus

MusclesMuscles

• Flight muscles account for 25 to 35 % of totalFlight muscles account for 25 to 35 % of total body mass of strong fliers

• With birds that rely more on running more• With birds that rely more on running more mass may be in the leg muscles than in flight

Li h d d k• Light and dark meat– Dark meat has the presence of myoglobin which i di hi h i f bi b liindicates a high capacity for aerobic metabolism

– Light meat has little capacity for aerobic t b limetabolism

Avian wingAvian wing

• Wing produces lift and forward motionWing produces lift and forward motion.

• Primaries are mostly responsible for propelling

S d i f lif• Secondaries for lift• Lift – vertical force 

equal or greater than theequal or greater than the

weight of the bird

• Drag – force that is opposed

f d f h b dto forward motion of the bird 

through the air

Avian WingAvian Wing

• Wing loadings (mass of the bird divided byWing loadings (mass of the bird divided by wing area)

FlightFlight

• http://wwwyoutube com/watch?v=ssrv89x7Qhttp://www.youtube.com/watch?v=ssrv89x7Q2U

• http://wwwyoutube com/watch?v=31Xw75h• http://www.youtube.com/watch?v=31Xw75hAwIc

h // b / h? QI fi9• http://www.youtube.com/watch?v=vQIsfi9vaeQ

Flight musclesFlight muscles

• Pectoralis – pulls pdown on wing

• Supracoracoideus –lift ilifts wing

• Both muscles originateBoth muscles originate on the sternum

Basic wing typesBasic wing types

• A) dynamic soaring – needs strong persistent wind) y g g p

• B) Elliptical – forest species for rapid, slow flight and high maneuverability

• C) High aspect ratio – typical of fast strong fliers

• D) High lift – static soarers, marked slotting in primaries, seek out rising air massesout rising air masses

Bird feetBird feet

• A) anisodactyl

• B) zygodactyl – toes 2 and 3 forward i.e. parrots and woodpeckers

• C) heterodactyl – toes 3 and 4 forward, only in trogons

• D) syndactyl – i e belted kingfisherD) syndactyl  i.e. belted kingfisher

• E) pamprodactyl all toes forward, swifts

BeaksBeaks

TonguesTongues

• Some woodpecker tonguesSome woodpecker tongues can be extended 4X the length of the beak havelength of the beak, have barbs on the end for impaling bugs in wood tunnelsbugs in wood tunnels

• Hummingbirds and sunbirds the tip of their tongue isthe tip of their tongue is divided into thin hairlike projections that nectarprojections that nectar adheres to by capillary force

Digestive systemDigestive system

• Crop – enlarged portion of theCrop  enlarged portion of the esophagus for temporary food storage also used to feedstorage, also used to feed nestlings, doves produce a nutritive fluid (crop milk) thatnutritive fluid (crop milk) that they regurgitate for their offspringoffspring 

Digestive systemDigestive system

• Stomach – 2 relatively distinct chambersStomach  2 relatively distinct chambers– Proventriculus – anterior glandular stomach

Gizzard posterior muscular stomach– Gizzard – posterior muscular stomach• A turkeys gizzard can crack nuts that require 50‐150 kg of pressure to breakp

• Gut length changes – birds that eat different types of food over different season can change the length of their gut. (also 

h i di ti )a change in digestive enzymes)

VisionVision

• Different eye shapes are basically a function ofDifferent eye shapes are basically a function of fitting a large eye in a small skull

HearingHearing

• For the most part birds hear about as well as humans, Owls p ,being the main exception.

• Owls have a facial ruff that acts as a parabolic sound reflector d th l h t i i th h f th ff dand they also have assymetries in the shape of the ruff and 

the skull

OlfactionOlfaction

• Most birds have a poorly developed sense of smellp y p

• Some exceptions

– Kiwi

– Turkey Vulture

VocalizationsVocalizations

• Bird songs are specifically the breeding calls of many bird g p y g yspecies

• It is a learned behavior

• Indigo Bunting

• http://www.learnbirdsongs.com/birdsong.php?id=19

• Wood Thrush• Wood Thrush

• http://www.learnbirdsongs.com/birdsong.php?id=32

• Lyre birdLyre bird

• http://www.youtube.com/watch?v=VjE0Kdfos4Y

• Paired with visual displays

• http://www.youtube.com/watch?v=ARVbLaYbSjo

• http://www.youtube.com/watch?v=bRQgYjKaGek

Mating systemsMating systems

• Two broad categoriesTwo broad categories– Monogamy

Polygamy– Polygamy

• Polygamy can be exhibited by:– Males = Polygyny

– Females = Polyandry

– Both sexes = Promiscuity

Social MonogamySocial Monogamy

• Share responsibility for clutch but have extra‐Share responsibility for clutch but have extrapair copulations

• Benefits for both sexes

– Increase fitness

– Increase heterozygosity

• Male benefits• Male benefits

– Sire more offspring

– Another male cares for his offspring

– Spreading reproductive investment

• Female benefits

– All eggs fertilizedgg

– Increase fitness mating with higher quality male

– Quasi nest parasitism

NestsNests

• Large variety in nests and nesting behaviorLarge variety in nests and nesting behavior

• Not all birds construct nests or even care for their own eggstheir own eggs

• Brood Parasites 

EggsEggs

• Oviparity – why haven’tOviparity  why haven t birds evolved viviparity?  Viviparity has evolvedViviparity has evolved many times and also in other sauropsids Whatother sauropsids.  What is the advantage of Oviparity in birds?Oviparity in birds?

OffspringOffspring

• Two main typesTwo main types– Precocial

Altricial– Altricial

MigrationMigration

• About 40% of bird species in Palearctic areAbout 40% of bird species in Palearctic are migratory

• Advantages = food resources avoid• Advantages = food resources, avoid temperature stress, longer summer activity periodsperiods

• Cues – internal rhythms and external stimulus– Day length – best indicator