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BirdsCopyright © McGraw-Hill Education
Characteristics of Birds• Birds have adaptations to generate their own body heat internally,
feathers, and lightweight bones.
• Many adaptations are designed around flight.
BirdsCopyright © McGraw-Hill Education
Characteristics of Birds
Endotherms• Birds are endotherms, which means they generate body heat
internally by their own metabolism.
• A high body temperature enables the cells in a bird’s flight muscles to use large amounts of ATP needed for rapid muscle contraction during flight.
BirdsCopyright © McGraw-Hill Education
Characteristics of Birds
Feathers• Birds are the only living animals to have feathers – specialized
outgrowths of the bird’s skin.
• Feathers have two main functions: flight and insulation.
BirdsCopyright © McGraw-Hill Education
Characteristics of Birds
Feathers• Feathers that cover the body, wings, and tail of a bird are called
contour feathers
• Down feathers are soft feathers located beneath the contour feathers.
• The preen gland secretes oil that adds a waterproof coating to the feathers.
BirdsCopyright © McGraw-Hill Education
Characteristics of Birds
Lightweight bones• A strong, lightweight skeleton allows birds to fly.
• The bones of birds are unique because they contain cavities of air.
• Large, powerful flight muscles attach to the sternum – breastbone, keel.
Flight
Animation
FPOAdd link animation from page 862 ( Figure 15) here.
BirdsCopyright © McGraw-Hill Education
BirdsCopyright © McGraw-Hill Education
Characteristics of Birds
Respiration• Flight muscles use a large amount of oxygen.
• When a bird inhales, oxygenated air moves through the trachea into posterior air sacs.
• When a bird exhales, deoxygenated air leaves the respiratory system and oxygenated air is sent to the lungs.
BirdsCopyright © McGraw-Hill Education
Characteristics of Birds
Circulation• A bird’s circulatory system
helps it maintain high levels of energy by efficient delivery of oxygenated blood to the body.
• Birds have a four-chambered heart.
BirdsCopyright © McGraw-Hill Education
Characteristics of Birds
Feeding and digestion• Birds require large amounts of food to maintain their high
metabolic rate.
• Many birds have a crop at the base of the esophagus that stores food.
• The gizzard contains small stones that crush food the birds have swallowed.
BirdsCopyright © McGraw-Hill Education
Characteristics of Birds
Excretion
• Bird kidneys filter wastes from the blood.
• Water is reabsorbed, and birds do not store urinary wastes due to its weight
BirdsCopyright © McGraw-Hill Education
Characteristics of Birds
The brain and senses• The cerebellum is large because birds need to coordinate
movement and balance during flight.
• The cerebrum controls eating, singing, flying, and instinctive behavior.
• Generally have excellent vision and hearing
BirdsCopyright © McGraw-Hill Education
Characteristics of Birds
Reproduction• All birds have internal fertilization.
• After fertilization, the amniotic egg develops and is encased within a hard shell.
• Birds incubate, or maintain favorable conditions, for their egg or eggs and feed the young after hatching.
BirdsCopyright © McGraw-Hill Education
Diversity of Modern Birds• Modern birds are divided into about 27 orders.
• Anatomical differences, specific behaviors, songs, and habitats distinguish the orders
BirdsCopyright © McGraw-Hill Education
Evolution of Birds
Feathered dinosaurs• Fossil evidence shows that birds evolved from the same line as
crocodiles and dinosaurs.
• Archaeopteryx was an ancient bird with a reptile-like tail, clawed fingers on the wings, teeth, and a body covered with feathers.
BirdsCopyright © McGraw-Hill Education
Ecology of Birds
Habitat destruction• Birds are important predators of small mammals, arthropods,
and other invertebrates.
• Disperse seeds
• Many birds are threatened by habitat destruction or degradation .
Illegal trade• Illegal pet-bird trade is increasing.• Exotic birds are taken from their natural habitats, which can
cause species to disappear.