Some interesting facts about birds are that they have no teeth and their bones are hollow. They are also the only animals on earth who have feathers.
Most birds can fly, but not all of them. Birds such as ostriches, kiwis, penguins and emus lack the power of flight. The ostrich is also the largest bird, and the fastest runner on two legs. It also lays the largest egg of any bird.
Most birds eat insects, but overall, birds eat just about anything. Some birds, such as vultures, eat carrion. Hummingbirds sip nectar, and toucans eat fruit. Penguins and cormorants eat fish, while birds of prey such as owls take small mammals and even other birds.
Birds such as starlings eat both animal and plant material. Owls also regurgitate the parts of their prey that they can't digest, such as bone and fur. These are called owl pellets, and they help biologists determine the owl's diet.
Even birds that don't fly have feathers. The different types of feathers are those designed for flight, designed to keep the bird warm and designed for courtship. Feathers designed for courtship include the tail of the peacock. It is also used for defense.
All birds lay hard-shelled eggs. Some birds lay eggs every day, whether the eggs are fertile or not. This can be seen in domestic chickens.