Birds Section 31.2

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

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

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”

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

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

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

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

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

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

Feathers

Feathers

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

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

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

Feathers

Rectrices – Light blue

Skeletal System cranium maxilla mandible sternum humerus carpals metacarpals

Skeletal System alula

Metacarpals Metacarpals

Humerus

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

How do Birds Fly?

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

Flight Requires Energy

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

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

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

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

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

2. 1. 3. 4.

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

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

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

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

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

Internal Anatomy

Internal Anatomy

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

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 http://www.youtube.com/watch?v=McunSYwfcoI

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

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