Classification: Kingdom Animalia, Phylum Chordata, Subphylum Vertebrata, Amniota, Class Aves

Characteristics of birds:

• feathers
• beak; no teeth (in modern birds - some fossil birds had teeth)
• 4 chambered heart
• endothermic
• pygostyle (in modern birds)
• uropygial (preen) gland (in most birds; a few groups have apparently lost this gland)
• syrinx

Relationships of birds to other animals:

• closest living relatives: crocodilians
• closest extinct relatives: (other) dinosaurs
• birds: "glorified reptiles"

Birds as flying machines: structural and behavioral adaptations

• weight reduction
• weight shifted to body center
• bone fusion - increased strength
• quick response time

Avian External Anatomy