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Class Aves – Birds

Class Aves – Birds. Birds are found in most every habitat from forests to deserts, even in caves. Some birds dive in the ocean to 45 m to catch prey. Birds have visited both the North & South poles. The bee hummingbird of Cuba weighs 1.8 g and is one of the smallest vertebrate endotherms.

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Class Aves – Birds

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  1. Class Aves – Birds • Birds are found in most every habitat from forests to deserts, even in caves. • Some birds dive in the ocean to 45 m to catch prey. • Birds have visited both the North & South poles. • The bee hummingbird of Cuba weighs 1.8 g and is one of the smallest vertebrate endotherms.

  2. Derived Characters of Birds • A bird’s most obvious adaptations for flight are its wings and feathers. • Feathers are the feature that set birds apart from other vertebrates.

  3. Characteristics of Birds • All birds also have hindlimbs adapted for walking, swimming, or perching. • Foot structure in bird feet shows considerable variation. • All have keratinized beaks. • All lay shelled amniotic eggs.

  4. Light Weight Skeleton • Frigate bird • 7 foot wing span • 4 ounce skeleton

  5. Adaptations for Flight • Enlarged sternum • Flight muscle attachment • Long neck • balance

  6. Pygostyle

  7. Skull • Most bones fused • Much lighter than reptile or mammal skull

  8. Adaptations for Flight • Wing • lift

  9. Form & Function – Feathers • Feathers are lightweight, yet tough, consisting of: • A hollow quill emerges from the skin. • This becomes the shaft which bears numerous barbs that form a flat, webbed surface, the vane. • Each barb contains many barbules.

  10. Adaptations for Flight • Feathers • Light weight • Strong

  11. Form & Function – Feathers • Contour feathers are vaned feathers that cover and streamline a bird’s body. • Called flight feathers if they extend beyond the body. • Down feathers are soft and have no hooks on barbules. • Filoplume feathers are hair-like – function unknown. • Powder-down feathers disintegrate as they grow, releasing powder that aids in waterproofing.

  12. Form & Function – Feathers • As a feather nears the end of its growth, keratin is deposited to make some of the structures hard. • The protective sheath surrounding the new feather splits open, and the feather unfurls.

  13. Form & Function – Feathers • When fully grown, feathers are dead – like mammalian hair. • Birds molt to replace worn out feathers. • Usually feathers are discarded gradually to avoid bare spots. • Flight feathers & tail feathers are lost in pairs to maintain balance. • Many water birds lose all their primary feathers at once and are grounded during the molt.

  14. Form & Function – Feathers • Colors in birds may be pigmentary or structural. • Red, orange, & yellow are colored by pigments called lipochromes. • Black, brown, & gray are produced by the pigment melanin. • Blue is created structurally by the scattering of shorter wavelengths of light by particles within the feather.

  15. Adaptations for Flight • Reduce body weight • No teeth • No urinary bladder • No penis • Only one ovary

  16. Flight • To fly, birds must generate lift forces greater than their own mass and they must provide propulsion to move forward. • Bird wings are designed to provide lift.

  17. Flight - Wings are Specialized for Particular Kinds of Flight • Elliptical wings are good for maneuvering in forests. • High speed wings are used by birds that feed during flight or that make long migrations. • Dynamic soaringwings are used by oceanic birds that exploit the reliable sea winds. • High lift wings are found in predators that carry heavy loads. Soaring over land with variable air currents.

  18. Migration • Sissor-tailed flycatchar • Migates to Central and South America in October • Returns in April

  19. Migration • Arctic tern • Migrates 25,000 miles!

  20. Migration • The stimulus for migration has to do with changing hormone levels brought about by a change in day length.

  21. Food & Feeding • Early birds were carnivorous, feeding mostly on insects. • Many birds are still insectivores. • Other foods include nectar, seeds, berries, worms, crustaceans, molluscs, fish, frogs, small birds & mammals.

  22. Food & Feeding • Some birds are generalists, feeding on a wide range of food items. • Perhaps more competition for food, but less danger of something happening to the food source. • Others are specialists, only feeding on one type of food. • Less competition, more danger of losing the food source.

  23. Food & Feeding • The beaks of birds are strongly adapted to specialized food habits.

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