Birds are a class of vertebrates, the Aves.
They are warm-blooded and lay eggs. Their bodies are covered with feathers and they have wings. Feathers have three functions: flight, temperature regulation and display. Most birds have hollow main bones with air sacs in them This makes them lighter and makes flight easier.
Birds are bipedal: they have two legs which are often covered with scales (small, flat plates which over-lap in the same way as feathers). They have a hard beak with no teeth.
Because birds keep a high body temperature, they use lots of energy. So, they need to eat a lot of food compared with their weight.
Chinese goose head at List of goose breeds, by Alan D. Wilson

elster bird birds

Shorebird

green woodpecker birds spring


Northern Cardinal

Red-crested pochard, by Diliff

Baltimore Oriole

Superb lyrebird, by Fir0002

Black swan, by Fir0002

Resting Australian pelicans, by JJ Harrison


source-www.allaboutbirds.
http://animals.nationalgeographic.com
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