EQ: What do birds have in common?

What is a bird? Reptile-like animals that maintains a constant internal body temperature Outer covering are feathers 2 legs and front limbs modified into wings

Feathers Made of mostly protein Develops from pits in the bird’s skin Help birds fly and keeps them warm Two types: Contour (provides the lifting force and balance needed for flight) Down (trap air close to the body and keeps the bird warm)

Evolution of Birds Evolved from extinct reptiles Most believed they evolved from dinosaurs Archaeopteryx (birdlike fossil) Dates back from Jurassic Period (150 million years ago) Has feathers like a bird, but also has teeth in its beak, a bony tail, and claws on wings

Body Temperature Controls Endotherms- Can generate their own body heat (unlike reptiles) Average body temperature of birds is 41⁰ C

Feeding: Bird Beaks Bird beaks/bills adapt to the type of food it eats Seed-eaters have short thick beaks Insect-eaters have short fine beaks Carnivorous birds have strong hook beaks

Feeding: Digestion Birds lack teeth, so they can’t chew food Crop- food stored here and is moistened Parent birds will regurgitate food from the crop After the crop, food goes into the stomach Carnivore birds have an expandable stomach Other birds have a gizzard (muscular organ that grinds the food)

Respiration Unique and highly efficient system One way flow Most air first enters air sacs (oxygen in) then to the lungs (Carbon Dioxide out) Allows birds to maintain their high metabolic rate (for flying) and temperature

Circulation 4 chambered hearts and 2 circulatory loops Complete separation of oxygen-rich blood and oxygen-poor blood

Excretion Similar to reptiles Wastes are removed by the kidneys Cloaca reabsorbs water, leaving waste in a white pasty form

Response Birds’ brains are relatively large for their bodies Cerebrum is large (controls behaviors such as flying, courtship, nesting, etc) Well developed eyes Can see in color (many can see better than humans) Taste and smell are not as developed

Movement Most can fly (those that don’t can run or swim) Birds’ skeletons are more rigid than reptiles Strengthened by internal struts Bones are filled with air spaces, making them lighter Large chest muscles for flying

Reproduction When ready to mate, sex organs grow larger until functional size Internal fertilization Bird eggs are similar to reptiles’ (amniotic eggs)

Groups of Birds (an overview) Nearly 30 different orders of birds Largest order is the passerines, over 5,000 species which includes finches, crows, sparrows, mockingbirds, and cardinals