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

Diet and feeding

The diet of woodpeckers consists mainly of insects and their grubs taken from living and dad 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 with a diet including ants, bird eggs, cactus fruits, lizards, nestlings, and insects. 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. 

The ability to excavate allows woodpeckers to obtain tree sap, an important source of food for some species. Most famously, the sapsuckers (genus Sphyrapicus) feed in this fashion, but the technique is not restricted to these, and others such as the acorn woodpecker and white-headed woodpecker also feed in this way. It was once thought that the technique was restricted to the New World, but Old World species, such as the Arabian woodpecker and great spotted woodpecker, also feed in this way. 

Breeding

All members of the family Picidae nest in cavities. Almost every species nest 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 produces 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 ad 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. This may come from other species of woodpecker, or other cavity nesting birds like swallows and starlings. Woodpeckers may aggressively harass potential competitors, and also use other strategies to reduce the chance of being usurped from their nesting site; for example the red-crowned woodpecker digs its nest in the underside of a small branch, which reduces the chance that a larger species will take it over and expand it. 

Members of Picidae are typically monogamous, with a few species breeding cooperatively and some polygamy reported in a few species. Polyandry, where a female raises two broods with two separate males, has also been reported in the West Indian woodpecker. A pair will work together to help built the nest, incubate the eggs and raise their altricial young. However, in most species the male does most of the nest excavation and takes the night shift while incubating the eggs. A nest will usually consist of 2-5 round white eggs. Since these birds are cavity nesters, their eggs do not need to be camouflaged and the white color helps that parents to see them in dim light. The eggs are incubated for about 11-14 days before the chicks are born. It takes about 18-30 days before the young are neady to leave the nest.