A group of living things
Birds
Aves
Living dinosaurs that grew feathers before they flew
Its members' last common ancestor lived about 95 million years ago.
You and birds last shared an ancestor about 320 million years ago (on 4 December, if life's history were one year).
The pigeon in your garden is a living dinosaur. Birds belong to the same big dinosaur group as Tyrannosaurus rex. When an asteroid struck about 66 million years ago, it wiped out all the other dinosaurs. Only the bird branch of the dinosaur family survived.
Feathers came before flight. Some small ground dinosaurs that could not fly already had simple coats or arm and tail feathers. Archaeopteryx mixed feathers and a wishbone with teeth, wing claws and a long bony tail.
Today there are about 11,000 kinds of birds. All living birds have feathers, wings, two legs and a toothless beak. Many have light, strong bones with hollow spaces. Beaks range from long probes to hooked tearers, and feathers range from plain browns to bright greens and reds. Most garden birds are between sparrow and crow size. You can find them on every continent, from forests to deserts and city streets.
Crocodile relatives
The closest living relatives of birds are crocodiles and their relatives such as alligators.
A giant sprinter
The flightless ostrich is the tallest and heaviest living bird. It stands up to about 2.7 metres tall and weighs up to about 150 kilograms. It can sprint at about 70 kilometres per hour and cover about 3 to 5 metres in one stride.
Longest journey
Arctic terns make the longest migration of any animal. They breed around Arctic coasts and tundra. Then they fly towards Antarctica and back, with one tracked bird covering about 96,000 kilometres.