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Birds (Class: Aves). Birds apparently evolved from reptiles during the Jurassic. The oldest known bird (Archaeopteryx) resembled reptiles in limb bones and other features. Birds still resemble reptiles: horny beaks, scaly legs, and egg-laying. Digestion of Birds. - PowerPoint PPT Presentation
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Birds (Class: Aves)Birds apparently evolved from reptiles during the Jurassic.The oldest known bird (Archaeopteryx) resembled reptiles in limb bones and other features.
Birds still resemble reptiles: horny beaks, scaly legs, and egg-laying.
Digestion of BirdsDigestive system is
often subdivided into functional regions
Specialization reflects feeding behavior
Video linkhttp://people.eku.edu/r
itchisong/birddigestion.html
Digestive Tract Specializations
Crop: in most birds; provides storage (largest in seed eaters); can produce “milk” containing fat & protein, but lacks sugar of mammalian milk. Production is stimulated by prolactin as in mammals.
Buccal cavity
esophagus
crop
proventriculus
gizzard
pylorusSmall intestine
Large intestine
cloaca
vent
Digestive Tract Specializations
Proventriculus: contains acids and enzymes.
Gizzard: often contains small pebbles or grit and is thick and muscular for grinding food.
Buccal cavity
esophagus
crop
proventriculus
gizzard
pylorusSmall intestine
Large intestine
cloaca
vent
Prey CapturePrey are captured primarily with beaks and feet.Raptors rely on talons to catch prey – not beaks!Beaks are toothless, preventing any processing in the mouth
Bill AdaptationsInsectivores
Perched Feeders: typically have short, thin, pointed bills (tweezer-like) for seizing insects.
Aerial Feeders: typically have short, weak beaks and a wide gape.
Bill Adaptations Mud Sifters like
Flamingos and Dabbling Ducks use their tongues and bills for prey capture. Both structures have horny projections (lamellae) and sensory corpuscles to scoop up water & mud and filter out the prey items.
Bill Adaptations Carnivorous Birds like ravens and roadrunners have heavy beaks to kill prey.Raptors like eagles, owls, falcons, and hawks use their talons to catch prey, but have a sharply hooked beak to tear off chunks of flesh. In
addition, falcons have a tomial tooth (sharp projection from the upper mandible matching a notch in the lower mandible.
Bill AdaptationsSeed Crackers like
cardinals have stout, heavy bills.
Fish eaters like pelicans, mergansers, and anhingas, have pouches, hooks, serrations, or spear-like bills to kill and grasp fish.
Bill AdaptationsSeed Pryers like
crossbills use the diverging ends of their bill to pry seeds out of pine cones.
Hammering is a technique used by chickadees and woodpeckers
Bill AdaptationsStrainers like
shovelers and spoonbills use widened bills and tongues to strain small particles out of water and mud. They are also considered mud sifters.
Bill AdaptationsProbers like many
shore birds have extremely long thin bills. Some of them are able to flex their bills backward (skull kinesis) to grasp crabs and other invertebrates from holes in mud or sand.