BIRDS

WHAT IS A BIRD?  Birds can maintain a constant internal body temperature. They have feathers, two legs covered with scales used for walking or perching. They have front limbs modified into wings.  Feathers are made of protein and develop in the birds’ skin. Feathers are important for flight and to keep the bird warm.  There are 2 types of feathers: contour and down feathers.

FORM, FUNCTION, AND FLIGHT  Birds have many different things that allow them to fly: they have a highly efficient digestive, respiratory, and circulatory system; aerodynamic feathers and wings; strong, lightweight bones; and strong chest muscles.

BODY TEMPERATURE CONTROL  Birds are endotherms. That means they can generate their own body temperature. Birds, mammals, and a few other animals have a high rate of metabolism. Metabolism are all of the chemical reactions inside an animal. This process produces heat.  A bird’s feathers insulate its body enough to conserve its metabolic energy keeping the bird warm.

FEEDING  The more food a bird eats, the more heat energy its metabolism can generate.  Small birds have to eat more than large birds because they lose heat faster.  Birds will have different beaks based on what they eat.  Insect eaters have short, fine bills.  Seed eaters have short, thick bills.  Carnivorous birds have strong hooked bills.  Nectar eaters have long, thin bills.  Fruit eaters have large, long bills.  Fish eaters have long, flat bills.

 Birds do not have teeth.  Birds have a crop – food is stored and moistened in the crop.  After the crop food moves to the stomach. Birds that eat insects and seeds have a gizzard to help them grind food down.  Food moves from the stomach to the small intestine.

RESPIRATION  When a bird inhales the air will enter large air sacs. Birds have a very effective respiratory system.  The respiratory system helps them to keep a high metabolic rate and maintain body temperature. A good respiratory system is also important for flight.

CIRCULATION  Birds have a 4 chambered heart with 2 separate loops.  They keep oxygen-rich and oxygen- poor blood completely separate.

RESPONSE  Birds have a well-developed sense system to help them with flight.  Birds have well developed eyes and see color very well. Most birds can also hear well.  Taste and smell is not well-developed in birds.

MOVEMENT  Some birds cannot fly but they get around by walking or running.  Most birds can fly.  They have bones that are fused together to make a rigid skeleton to help fly.  Bird bones are lightweight. They have large chest muscles.

REPRODUCTION  Birds lay amniotic eggs like reptiles but they have a hard outer shell.  Most birds will incubate their eggs until they hatch.

GROUPS OF BIRDS  There are a large variety of birds.  The largest order of birds are passerines or perching birds.  Pelicans and their relatives – found in aquatic ecosystems. All have 4 toes connected by a web.  Parrots – colorful, noisy, use feet to hold food.  Birds of prey – good predators with hooked bills, large wingspans, and sharp talons.  Cavity-nesting birds – these birds live in holes they make in trees, mounds, or underground tunnels  Herons and relatives – adapted to wade in water.  Ostriches and relatives – flightless birds that must move by running or swimming.

ECOLOGY OF BIRDS  Some birds are important for pollinating – like a hummingbird.  Some birds are important for seed dispersal – they will eat seeds but not digest them so the seeds come out in the droppings.  They can control insect populations.  Many birds migrate.  They can help indicate if there is a problem in the environment.