Woodpecker

The woodpeckers are part of the Picidae family, a group of near-passerine birds that also consist of piculets, wrynecks, and sapsuckers. 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 although there has been speculation recently that these species may still exist.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, theirmorphology 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. Many of the foraging, breeding and signaling behaviors of woodpeckers involve drumming and hammering using the bill. To prevent brain damage from the rapid and repeated impacts, woodpeckers have evolved a number of adaptations to protect the brain. These include small brain size, the orientation of the brain within the skull which maximises the area of contact between the brain and the skull and the short duration of contact. The millisecond before contact with wood a thickened nictitating membrane closes, protecting the eye from flying debris. The nostrils are also protected; they are often slit-like and have special feathers to cover them. Woodpeckers, piculets and wrynecks all possess zygodactyl feet. Zygodactyl feet consist of four toes, the first hallux and the fourth facing backward and the second and third facing forward. This foot arrangement is good for grasping the limbs and trunks of trees. Members of this family can walk vertically up a tree trunk, which is beneficial for activities such as foraging for food or nest excavation.