Chapter 15.1a Birds

Bird Characteristics Birds can be found in the air, on land, and in water. They are very diverse. They can be very large, like an ostrich, or very small, like a humming bird. They live all over the world. They have different diets of meat, fish, insects, fruit, seeds, or nectar. They all have feathers and scales and lay eggs.

Bird Eggs Birds lay amniotic eggs with a hard shell. This egg is important for provided a protective environment for the embryo. The shell is made of calcium carbonate. Birds have internal fertilization. The female will lay one or more eggs at a time. A group of eggs is called a clutch. One or both parents will keep the eggs warm, or incubate them. The young is cared for by one or both parents.

Flight Adaptations Birds have almost hollow bones. They are able to fly because of this and because they have wings, feathers, strong flight muscles, and a good respiratory system. They also have good eyesight and are able to make large amount of energy.

Hollow Bones Many bones of some birds are joined together. This gives more strength and stability for flight. Most bones are almost hollow with cross braces to strengthen the bones. The hollow spaces are filled with air. They have a large sternum, or breastbone that supports the muscles needed for flight. The end of the spine supports tail feathers. The tail is important for steering and balance during flight and landing.

Feathers Birds are the only animals that have feathers. They have 2 types of feathers: Contour feathers – these give the bird coloring and a smooth shape. They are also used in flight. Down feathers – provide insulation next to the skin of adult birds and cover the bodies of young birds. Birds are endotherms – they control their own body temperature. Feathers are important for doing this. Feathers grow from follicles. A feather is a shaft with many branches called barbs and each branch has branches called barbules. Birds have an oil gland near the tail. They will rub oil from that gland over its feathers. This is called preening. The oil is important for helping the feathers last longer and making them waterproof.