Birds are feathered vertebrates, bipedal creatures with their front pair of legs modified into wings. They have a number of distinctive features, many of them related to flight:

Birds are intelligent and social creatures, capable of using tools, communicating with complex vocalizations and movements, and providing extensive parental care to their young. They share a number of features with dinosaurs, and in fact are the only living members of that ancient group.

There are two broad types of living birds – flightless birds and so-called modern birds.

Flightless Birds
The Paleognathae, or “old-jawed” birds, are mostly flightless. Their bodies are modified for running, with long necks and legs and simplified wing bones. This group includes the ostriches, kiwis, rheas, tinamous, emus, and cassowaries.

Modern Birds
The Neognathae, or “new-jawed birds,” includes all of the other birds from songbirds to raptors to fowl to penguins. There are approximately 10,000 species incorporating a stunning range of form and behavior.

Variations in the plumage, beaks, and feet are especially notable and reflect differences in diet, social structure, and flying ability.

Birds are among the most well-travelled migratory animals. Although some move only short distances to take advantage of microclimate differences, others perform feats that require staggering amounts of endurance and an amazing ability to navigate.

Bar-tailed godwits have been tracked flying nearly 6500 miles without landing. Shearwaters make a 40,000 mile roundtrip every year from New Zealand to Alaska and back.