Woodpecker

The woodpeckers, piculets, wrynecks, and sapsuckers are a family, Picidae, of near-passerine birds. Members of this family are found worldwide, except for Australia, New Guinea, New Zealand, Madagascar, and the extreme polar regions. Most species live in forests or woodland habitats, although a few species are known to live in treeless areas, such as rocky hillsides and deserts.
The Picidae are just one of eight living families in the order Piciformes. Other members of Piciformes, such as the jacamars, puffbirds, barbets, toucans, and honeyguides, have traditionally been thought to be closely related to the woodpeckers, piculets, wrynecks, and sapsuckers. More recently, DNA sequence analyses have confirmed this view.

There are about 200 species and about 30 genera in this family. Many species are threatened or endangered due to loss of habitat or habitat fragmentation. Two species of woodpeckers, the ivory-billed woodpecker and the imperial woodpecker, have been considered extinct for about 30 years.
Members of the family Picidae have strong bills for drilling and drumming on trees and long sticky tongues for extracting food. Woodpecker bills are typically longer, sharper and stronger than the bills of piculets and wrynecks; however, their morphology is very similar. The bill's chisel-like tip is kept sharp by the pecking action in birds that regularly use it on wood. Species of woodpecker and flicker that use their bills in soil or for probing as opposed to regular hammering tend to have longer and more decurved bills. Due to their smaller bill size, many piculets and wrynecks will forage in decaying wood more often than woodpeckers. The long sticky tongues, which possess bristles, aid these birds in grabbing and extracting insects deep within a hole of a tree. It had been reported that the tongue was used to spear grubs, but more detailed studies published in 2004 have shown that the tongue instead wraps around the prey before being pulled out.
The diet of woodpeckers consists mainly of insects and their grubs taken from living and dead trees, and other arthropods, along with fruit, nuts and sap from live trees. Ecologically, they help to keep trees healthy by keeping them from suffering mass infestations. 

The family is noted for its ability to acquire wood-boring grubs using their bills for hammering, but overall the family is characterized by its dietary flexibility, with many species being both highly omnivorous and opportunistic. The insect prey most commonly taken are those found inside tree trunks, whether they are alive or rotten, and in crevices in the bark. These include beetles and their grubs, ants, termites, spiders, and caterpillars. These may be obtained either by gleaning or, more famously, by excavating wood. Having hammered a hole into the wood, the prey is excavated by a long barbed tongue. Woodpeckers consume beetles that burrow into trees, removing as many as 85 percent of emerald ash borer larvae from individual ash trees.
All members of the family Picidae nest in cavities. Almost every 

species nests in tree cavities, although, in deserts, some species nest inside holes in cactus and a few species nest in holes dug into the earth. Woodpeckers also excavate nest holes in residential and commercial structures as well as wood utility poles. Woodpeckers and piculets will excavate their own nests, but wrynecks will not. The excavated nest is usually only lined from the wood chips produced as the hole was made. Many species of woodpeckers excavate one hole per breeding season, sometimes after multiple attempts. It takes around a month to finish the job. Abandoned holes are used by other birds and mammals that are secondary cavity nesters.] Because nesting holes are in great demand by other cavity nesters, woodpeckers face competition for the nesting sites they excavate from the moment the hole becomes usable.