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From Citizendium, the Citizens' Compendium

Birds are a class of animals (aves) that can be distinguished from all other living animals by the presence of feathers. They are two-legged, warm-blooded vertebrates with wings and they range greatly in size, the tiniest can fit on the palm of a human hand and the largest can be ridden upon. The largest living bird species (the Ostriches are flightless. Flight does not distinguish birds, because many insects have wings and can fly.

Birds reproduce by laying eggs, as do reptiles and amphibians.

There are more than 9,000 different bird species.

Contents 1 Types of bird 1.1 Birds of Prey (raptors) 1.2 Waterfowl 1.3 Flightless birds

Types of bird

Birds of Prey (raptors)

These include eagles and owls.

Waterfowl

Ducks, geese and swans are examples of waterfowl.

Flightless birds

Include ostriches, emus, penguins and puffins.