Woodpeckers are birds that belong to the family Picidae.
They are members of the order Piciformes.
Woodpeckers have many physical characteristics that make it easy for them to for live in and obtain food from trees.
There are more than 200 species of woodpecker in the world.
Woodpeckers can be found in most parts of the world. There are no woodpeckers living in the wild in Australia, New Zealand, Madagascar or Antarctica.
They live in forests, grasslands - including savannas - and scrublands. Some species live in deserts.
Woodpeckers mostly eat insects, insect larvae and spiders that live in trees. They may also eat fruit, nuts or sap.
Woodpeckers range in size from about 3 ¼ inches to almost two feet long.
The world's smallest woodpecker is the bar-breasted piculet.
Until 1958, the largest woodpecker on Earth was the imperial woodpecker. It has not been seen since then and may be extinct. It was about 2 feet long
The ivory-billed woodpecker, another large woodpecker, which was about 20 inches long, may also be extinct.
Most woodpeckers have some combination of black, white, brown, green or red feathers.
Like all Piciformes, woodpeckers have zygodactylous feet. Each foot has two toes pointing forward and two toes pointing backwards. This makes it easy for woodpeckers to climb up and down tree trunks.
Other Piciform characteristics that woodpeckers share include a strong beak, a long, sticky tongue, and a layer of cartilage between the beak bones and the rest of the skull that cushions the skull when the woodpecker taps on trees.
A woodpecker's tongue has a barb at the tip.
The woodpecker will use its strong, chisel-like beak to hammer a hole into a tree trunk and then use its long, sticky, barbed tongue to extract insects, larvae, spiders and sometimes tree sap.
A woodpecker that eats tree sap is known as a sapsucker.
Acorn woodpeckers store acorns in holes that they drill in trees with their beaks.
Woodpeckers have strong, stiff tail feathers. A woodpecker will use its tail as a prop to help it climb up and down vertical surfaces.
Like other Piciformes, woodpeckers communicate by drumming, tapping their bills against hollow structures such as tree trunks, telephone poles or hollow walls.
Their tapping sometimes causes damage to buildings.
All woodpeckers use holes as nests. Most drill nest holes in trees. Some species build their nests in cavities the ground. Some desert species build their nests inside cactuses.
Sometimes woodpeckers will build their nests in vertical human-made structures, such as buildings, fence posts and telephone poles.
A woodpecker will drill a new nest hole each year, and other bird species will build nests in nest holes that have been abandoned by woodpeckers.