1. 31.2 Section Objectives – page 826
Unit 3 Objectives:
Objective 1: Describe the evolutionary origin of Modern Birds
Objective 2: Describe basic characteristics of Modern Birds
Objective 3: Explain the form and function of the types of bird wings and the types of beaks/bills.
Objective 4: Describe the reproductive strategies for birds
Objective 5-7: Identify common examples of each of the orders of birds.
Objective 8: Student Presentation of Birds.
31.2 Section Objectives – page 826

2. Section 31.2 Summary – pages 826 - 833
What is a bird?
Birds inhabit a variety of environments around the world, including Antarctica, deserts, and tropical rain forests.
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3. Section 31.2 Summary – pages 826 - 833
What is a bird?
Fossil evidence seems to indicate that birds have evolved from small, two-legged dinosaurs called theropods.
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4. Section 31.2 Summary – pages 826 - 833
Origin of Birds
Fossil finds in China support the idea that birds evolved from a theropod dinosaur.
-Paleognathae: The large flightless ostrich-like birds and the kiwis, often called ratite birds, which have a flat sternum with poorly developed pectoral muscles.
-Neognathae: Flying birds that have a keeled sternum on which powerful flight muscles insert.
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5. Section 31.2 Summary – pages 826 - 833
Origin of Birds
Most scientists studying the origins of birds hypothesize that feathers evolved before flight.
Feathers aren’t the only features shared by modern birds and some theropod dinosaurs.
Both also have a sternum, a wishbone, shoulder blades, flexible wrists, and three fingers on each hand.
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6. Section 31.2 Summary – pages 826 - 833
Origin of Birds
Scientists hypothesize that today’s birds are derived from an evolutionary line of dinosaurs that did not become extinct.
At first, scientists thought that Archaeopteryx was a direct ancestor of modern birds; however, some paleontologists now think that it most likely did not give rise to any other bird groups. (About the size of a crow)
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7. Section 31.2 Summary – pages 826 - 833
Parrots, lories, and cockatoos 340 species
Origin of Birds
Owls species
Perching Birds species
Herons, bitterns, and ibises species
Woodpeckers, toucans, and honey guides species
Hawks, eagles, and falcons species
Archaeopteryx
Swans, geese, and ducks species
Penguins species
Theropod dinosaur
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8. Section 31.2 Summary – pages 826 - 833
What is a bird?
Like reptiles, birds have clawed toes and protein scales on their feet.
Fertilization is internal and shelled amniotic eggs are produced in both groups.
Although some birds are flightless, all birds have feathers and wings.
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9. Section 31.2 Summary – pages 826 - 833
Birds have feathers
A feather is a lightweight, modified protein scale that provides insulation and enables flight.
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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.
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11. 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.
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Birds have wings
A second adaptation for flight in birds is the modification of the front limbs into wings.
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13. 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.
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14. Section 31.2 Summary – pages 826 - 833
Flight
Wings
Hollow bones
For birds, the ability to fly is the result of complex selective pressures that led to the evolution of many adaptations.
Beaks
Air Sacs
Legs
Digestion
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15. Wing Types
-Elliptical wings: birds such as flycatchers, warblers, doves, woodpeckers, and magpies, which must maneuver in forested or brushy habitats
-High aspect ratio wings: birds that feed during flight such as swallows, hummingbirds, and swifts, or those that make long migrations, such as plovers, sandpipers, terns, and gulls; sweep back and taper to a slender tip
-Dynamic soaring wings: oceanic soaring birds, including albatrosses, shearwaters, and gannets, also have high aspect ratio wings shaped like those of sailplanes. They have long narrow wings, long wingspan, free ride, riding air, a type of flight that involves riding wind differentials
-High lift wings: hawks, vultures, eagles, owls, and ospreys, predators that carry heavy loads

16. 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.
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17. 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.
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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.
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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
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20. 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
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21. 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
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22. 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
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23. 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
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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.
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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.
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Birds are endotherms
Birds can live in all environments, from the hot tropics to the frigid Antarctic.
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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.
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Reproduction in birds
The eggs are turned periodically so that they develop properly.
In some species of birds, both parents take turns incubating eggs; in others, only one parent does so.
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Reproduction in birds
Bird eggs are distinctive, and often the species of bird can be identified just by the color, size, and shape of an egg.
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30. 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.

31. More Vocab Continue (Obj 4)
-Lek: In many species of grouse, males gather in a collective display ground called a Lek. This is divided into individual territories, each vigorously defended by a displaying male. Usually there is a dominant male and several subordinate males in a lek. Competition among males for females is intense, but females appear to choose the dominant male for mating because social rank correlates with genetic quality.
-Incubation: All birds lay eggs that must be incubated by one or both parents. Incubation is process of keeping eggs warm, turning them routinely, and protecting them from predators.
-Nest Parasites: Species which lay their eggs in the nests of other species. The other species then will incubate and rear the offspring of the parasite as their own. Examples include the Brown-Headed Cowbird and the European Cuckoo which build no nests at all.

32. Section 31.2 Summary – pages 826 - 833
Diversity of Birds
Birds are all very much alike in their basic form and structure.
In spite of the basic uniformity of birds, they do exhibit specific adaptations, depending on the environment in which they live and the food they eat.
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Diversity of Birds
The shape of a bird’s beak or bill gives clues to the kind of food the bird eats.
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Diversity of Birds
Hummingbirds, for example, have long beaks that are used for obtaining nectar from flowers.
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Diversity of Birds
Hawks have curved beaks that are adapted for tearing apart their prey.
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Diversity of Birds
Pelicans have huge bills with pouches that they use as nets for capturing fish.
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Diversity of Birds
The short, stout beak of a cardinal is adapted to cracking seeds.
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38. Beak/Bill Types