Birds are warm-blooded vertebrates from the class Aves, characterized by their laying of eggs with hard shells and for having feathers, toothless beaks, hearts with four chambers, and lightweight skeletons. Birds are also known as avian dinosaurs, which isn't just a coincidence--birds are the closest living descendants of the dinosaurs! Birds can be found almost anywhere on the earth and include species that range in size from the 5 cm tall hummingbird all the way to the 2.75 m tall ostrich.
Ravens are some of the most intelligent animals in the world, on par with chimpanzees and even toddlers.
It's estimated that about 20% of bird species migrate every year.
Ostriches are the largest bird in the world and have the largest eyes of any land animal. They also lay the largest eggs of any bird and can run up to 97 kph.
Birds' skeletons are made up of ultra-light, hollow bones.
Hummingbirds are the only bird that can both hover in place and fly backwards. Most species weigh less than a US nickel.
It's estimated that there are between 9,000 and 10,000 species of birds, with about 95% of them having been classified and described.