1. Birds
Section 31.2

2. Animal Classification
Sponges
Cnidarians
Worms
Mollusks
Arthropods
Echinoderms
Invertebrates
Class Aves
Animals
Fishes
Amphibians
Reptiles
Ectotherms
(cold-blooded)
Vertebrates
Birds
Mammals
Endotherms
(warm-blooded)

3. What is a Bird? Class Aves
Birds inhabit a variety of environments around the world including Antarctica, deserts, and tropical rain forests

4. What is a Bird? Birds are known as feathered dinosaurs
Birds evolved from small, two-legged dinosaurs called theropods
Like reptiles, birds have clawed toes and protein scales on their feet
Theropod
Ar·chae·op·ter·yx
Archaeopteryx “ancient wing”

5. What is a Bird?
Although some birds are flightless, all birds have feathers and wings
Cassowary
Kiwi
Emperor Penguins

6. Feathers
Feather – a lightweight, modified protein scale that provides insulation and enables flight
Preening – the process of birds cleaning its feathers

7. Feathers
During preening, a bird also uses its bill or beak to rub oil from a gland near the tail onto the feathers
This helps feathers last longer

8. Feathers Even with good care, feathers wear out and must be replaced
Molting – the shedding of old feathers and the growth of new ones
Most birds molt in late summer

9. Feathers
Most birds do not lose their feathers all at once and are able to fly while they are molting
Wing and tail feathers are usually lost in pairs so that the bird can maintain its balance and flight

10. Feathers Contour feather – used for flight
Down feather – used for insulation
Barbs – interlocking sections on feathers
Shaft
Down

11. Feathers

12. Feathers

13. Feathers
Coverts – The small feathers that cover the base of other feathers on a bird’s body, thereby filling in the plumage

14. Feathers
Alula – A bird’s “thumb”; small stiff feathers on the 1st digit of a bird's wing

15. Feathers Flight feathers of the wings Tail feathers Primaries
Secondaries
Tertiaries
Tail feathers
Rectrices

16. Feathers

17. Rectrices – Light blue

19. Skeletal System cranium maxilla mandible sternum humerus carpals
metacarpals

20. Skeletal System
alula

21. Metacarpals
Metacarpals

22. Humerus

23. Wings Sternum – breastbone
Powerful flight muscles are attached to the sternum and to the upper bone of each wing

24. How do Birds Fly?

25. Flight Requires Energy
A bird’s four-chambered, rapidly beating heart moves oxygenated blood quickly throughout the body
A chickadee’s heart beats 1000 times a minute
A human’s heart beats 70 times a minute at rest

26. Flight Requires Energy

27. Flight Requires Energy
A bird’s respiratory system supplies oxygenated air to the lungs when it inhales as well as when it exhales
A bird’s respiratory system consists of lungs and anterior and posterior air sacs

28. Flight Requires Energy
During inhalation, oxygenated air passes through the trachea (windpipe) and into the lungs
Most of the air passes directly into the posterior air sacs

29. Flight Requires Energy
When a bird exhales deoxygenated air from the lungs, oxygenated air returns to the lungs from the posterior air sacs

30. Flight Requires Energy
At the next inhalation, deoxygenated air in the lungs passes into the anterior air sacs

31. Flight Requires Energy
Finally, at the next exhalation, air passes from the anterior air sacs out of the trachea

32. 2. 1. 3. 4.

34. Endotherms
Endotherm – an animal that maintains a nearly constant body temperature that is not dependent on the environmental temperature
Birds are able to maintain the high energy levels needed for flight because they are endotherms

35. Endotherms Feathers reduce heat loss in cold temperatures
The feathers fluff up and trap a layer of air that limits the amount of heat lost

36. Endotherms
Responses to high temperatures include flattening the feathers and holding the wings away from the body
Birds also pant to increase respiratory heat loss

37. Endotherms
Birds and other endotherms must eat large amounts of food to sustain these higher levels of energy
Endotherms have higher metabolisms than ectotherms

38. Obtaining Food
There’s a direct relationship between a bird's beak and its ability to find food and survive in a given environment

39. Internal Anatomy

40. Internal Anatomy

41. Reproduction
Fertilization is internal and shelled amniotic eggs are produced in birds and reptiles
All females have cloacas whereas most males have cloacas
During copulation (mating), a male and female align their cloacas so sperm can enter the female

42. Reproduction A small amount of male birds have phalluses
Examples: ducks, chickens, and ostriches
Birds eggs are encased in a hard shell, unlike the leathery shell of a reptile
Ostrich Mating Ritual

43. Reproduction Incubate – birds sit on their eggs to keep them warm
The eggs are turned periodically so that they develop properly

44. Reproduction
In some species, both parents take turns incubating eggs; in others, only one does so