1. Section 31.2 Summary – pages 826 - 833
Birds have feathers
A feather is a lightweight, modified protein scale that provides insulation and enables flight.
Section 31.2 Summary – pages

2. Section 31.2 Summary – pages 826 - 833
Birds have feathers
Preening, keeps the feathers in good condition for flight.
During preening, a bird also uses its bill or beak to rub oil from a gland near the tail onto the feathers.
This is especially important for water birds as a way to waterproof the feathers.
Section 31.2 Summary – pages

3. Section 31.2 Summary – pages 826 - 833
Birds have feathers
The shedding of old feathers and the growth of new ones is called molting.
Most birds molt in late summer. However, most do not lose their feathers all at once and are able to fly while they are molting.
Section 31.2 Summary – pages

4. Section 31.2 Summary – pages 826 - 833
Birds have wings
A second adaptation for flight in birds is the modification of the front limbs into wings.
Section 31.2 Summary – pages

5. Section 31.2 Summary – pages 826 - 833
Birds have wings
Powerful flight muscles are attached to a large breastbone called the sternum and to the upper bone of each wing.
The sternum supports the enormous thrust and power produced by the muscles as they move to generate the lift needed for flight.
Section 31.2 Summary – pages

6. Section 31.2 Summary – pages 826 - 833
Flight requires energy
Flight requires high levels of energy.
Several factors are involved in maintaining these high energy levels.
Section 31.2 Summary – pages

7. Section 31.2 Summary – pages 826 - 833
Flight requires energy
First, a bird’s four-chambered, rapidly beating heart moves oxygenated blood quickly throughout the body.
This efficient circulation supplies cells with the oxygen needed to produce energy.
Section 31.2 Summary – pages

8. Section 31.2 Summary – pages 826 - 833
Flight requires energy
Second, 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.
Section 31.2 Summary – pages

9. Section 31.2 Summary – pages 826 - 833
Key: Breathing cycles
Flight requires energy
Cycle 1
Cycle 2
Inhalation 1
Inhalation 1
Exhalation 2
Exhalation 2
Trachea
During inhalation, oxygenated air passes through the trachea and into the lungs, where gas exchange occurs.
Anterior air sacs
Lung
Anterior air sacs
Posterior air sacs
Section 31.2 Summary – pages

10. Section 31.2 Summary – pages 826 - 833
Key: Breathing cycles
Flight requires energy
Cycle 1
Cycle 2
Inhalation 1
Inhalation 1
Exhalation 2
Exhalation 2
Trachea
Most of the air, however, passes directly into the posterior air sacs.
Anterior air sacs
Lung
Anterior air sacs
Posterior air sacs
Section 31.2 Summary – pages

11. Section 31.2 Summary – pages 826 - 833
Key: Breathing cycles
Flight requires energy
Cycle 1
Cycle 2
Inhalation 1
Inhalation 1
Exhalation 2
Exhalation 2
Trachea
When a bird exhales deoxygenated air from the lungs, oxygenated air returns to the lungs from the posterior air sacs.
Anterior air sacs
Lung
Anterior air sacs
Posterior air sacs
Section 31.2 Summary – pages

12. Section 31.2 Summary – pages 826 - 833
Key: Breathing cycles
Flight requires energy
Cycle 1
Cycle 2
Inhalation 1
Inhalation 1
Exhalation 2
Exhalation 2
Trachea
At the next inhalation, deoxygenated air in the lungs passes into the anterior air sacs.
Anterior air sacs
Lung
Anterior air sacs
Posterior air sacs
Section 31.2 Summary – pages

13. Section 31.2 Summary – pages 826 - 833
Key: Breathing cycles
Flight requires energy
Cycle 1
Cycle 2
Inhalation 1
Inhalation 1
Exhalation 2
Exhalation 2
Finally, at the next exhalation, air passes from the anterior air sacs out of the trachea. Thus, air follows a one-way path in a bird.
Trachea
Anterior air sacs
Lung
Anterior air sacs
Posterior air sacs
Section 31.2 Summary – pages

14. Section 31.2 Summary – pages 826 - 833
Birds are endotherms
Birds are able to maintain the high energy levels needed for flight because they are endotherms.
An endotherm is an animal that maintains a nearly constant body temperature that is not dependent on the environmental temperature.
Section 31.2 Summary – pages

15. Section 31.2 Summary – pages 826 - 833
Birds are 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.
Responses to high temperatures include flattening the feathers and holding the wings away from the body.
Birds also pant to increase respiratory heat loss.
Section 31.2 Summary – pages

16. Section 31.2 Summary – pages 826 - 833
Reproduction in birds
Birds reproduce by internal fertilization and lay amniotic eggs usually inside a nest.
Bird eggs are encased in a hard shell, unlike the leathery shell of a reptile.
Birds do not leave the eggs to hatch on their own. Instead, birds incubate or sit on their eggs to keep them warm.
Section 31.2 Summary – pages

17. Reproduction Vocabulary (Obj 4):
-Monogamy: An individual has only one mate (Bald eagles). 90% of bird species are monogamous.
-Polygamy: An individual has more than one mate during a breeding period.
-Polygyny: A breeding strategy in which (typically) one male will mate with more than one female during a breeding season.
-Polyandry: An individual has more than one mate during a breeding period. Typically one female will mate with more than one male during a breeding season. Practiced by several shorebird species including spotted sandpipers.

18. Section 31.2 Summary – pages 826 - 833
Diversity of Birds
The shape of a bird’s beak or bill gives clues to the kind of food the bird eats.
Section 31.2 Summary – pages

19. Section 31.2 Summary – pages 826 - 833
Diversity of Birds
Hummingbirds, for example, have long beaks that are used for obtaining nectar from flowers.
Section 31.2 Summary – pages

20. Section 31.2 Summary – pages 826 - 833
Diversity of Birds
Hawks have curved beaks that are adapted for tearing apart their prey.
Section 31.2 Summary – pages

21. Section 31.2 Summary – pages 826 - 833
Diversity of Birds
Pelicans have huge bills with pouches that they use as nets for capturing fish.
Section 31.2 Summary – pages

22. Section 31.2 Summary – pages 826 - 833
Diversity of Birds
The short, stout beak of a cardinal is adapted to cracking seeds.
Section 31.2 Summary – pages

23. Beak/Bill Types