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Birds (Aves)

Birds come in all shapes and sizes but they all have certain traits in common.

They have feathers instead of hair or fur. They are the only animal group that has feathers.
They have beaks or bills and no teeth.
They have two feet and two wings.
They are warm blooded.
They do not have live young like mammals, but lay eggs.
Most birds take care of their young, feeding them until they are old enough to find their own food.
Most birds build some kind of nest.
Birds have good eyesight and can see colors.
Most birds can fly. They have hollow bones to make their skeleton lighter for flight. They have large developed chest muscles for flight.
Birds can survive cold temperatures because they have an underlying layer of down feathers that act as thermal insulation, like wearing a down jacket!
Male birds are often (but not always) much more brightly colored than females. This is called sexual dimorphism. Females are often dull colored to blend in (camouflage) while nesting.
Some birds eat meat (rodents, fish, other birds or carrion). Some are seed eaters and some eat plants.
Many birds travel to a cooler climate for reproducing and summer feeding, and then return to a warmer climate for the winter. Moving from place to place like this is called migration.
Birds sing to attract a mate or mark a territory.
Not all birds can fly!