What is a bird? The answer is simple – a feathered animal!
Feathers are found in all birds, yet no other animals have them. The discovery of fossils of small feathered dinosaurs revealed that birds are the only surviving descendants of those animals that dominated life on Earth for over 100 million years.
Feathers probably evolved as a covering to keep birds warm, because like the mammals (including humans), birds are ‘warm-blooded’.
But most birds also need to fly, so their covering must be light-weight.
Indeed, feathers are the lightest natural material for their size.
The wings of birds, unlike those of bats and insects, are formed by feathers, which overlap and stop air from leaking through when a bird flaps during flight.
The feathers of penguins are very short as they cannot fly, and baby birds have soft ‘down’ which are feathers that lack a shaft or quill.
Text © Richard Noske 2019 CC BY-NC-SA