Woodpecker Biology and Behavior:

Biology | Drumming | Diet | Roosting and Nesting | Foraging



Biology

Contrary to popular opinion, woodpeckers do not get headaches from banging on trees. They have thickened skulls and powerful neck muscles that enable them to deliver sharp blows without damaging their organs. Their stout, chisel-like bills allow them to bore into wood. The tongue of a woodpecker, often covered with barbs or sticky saliva, can be extended a considerable distance in order to dislodge ants and insect larvae from deep crevices in wood and bark. For storage, the tongue is curled around the back of the head between the skull and skin.







Hairy Woodpecker (left) & Downy Woodpecker (right)



The tongue varies according to the woodpecker's diet and mode of foraging. Woodpeckers that excavate deeply into timber, such as the Pileated, have shorter tongues with spear-like tips bearing backward-facing barbs. Woodpeckers foraging mainly on the ground, such as the Northern Flicker, have tongues with flattened tips. Sapsuckers have brush-like tongues that hold the sap of trees by capillary action. Species that feed from crevices and surfaces of trees usually have longer tongues with bristles concentrated at the tip.



Most songbirds have three forward-facing toes and one backward-facing toe. Most woodpeckers, however, have two toes facing forward and one facing back. This is known as a zygodactyl foot and allows woodpeckers to easily climb and grasp trees and other structures. Woodpeckers move up a tree by hopping and depend on their especially stiff tail feathers to serve as a prop. They work their way up a tree, peering and poking into every nook and cranny, and then either fly in an undulating fashion to a new area or glide down to a neighboring tree to begin their foraging anew.







Northern Flicker

Most species of woodpeckers are sexually dichromatic -- the plumage markings differ between males and females. Males can be distinguished from females by the presence of a malar stripe ("moustache"), or by a red patch on the crown or throat area.



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Drumming

Drumming is the term given to a woodpecker's habit of hammering loudly and rapidly onto some resonating surface, such as a dying tree, stop sign, chimney, or house. Since woodpeckers do not have a song as do passerine birds, drumming may serve as a territorial signal similar to bird song and it may also serve to attract a mate. Both sexes are known to drum.



Listen to the drumming of a Pileated Woodpecker »



Diet

The diet of woodpeckers consists mainly of insects, berries, nuts, and seeds collected from trees and shrubs. Northern Flickers can be found feeding on ground insects such as ants. Sapsuckers drill very small holes in trees to feed on sap. Though woodpeckers can perform a great service by eating insects harmful to trees, such as woodborers and bark lice, they can become a pest when they begin tapping on houses, buildings, and utility poles. Woodpeckers drill holes for a variety of reasons, mainly to build nesting and roosting cavities, while foraging for insects, and when performing the activity known as drumming.







Yellow-bellied Sapsucker

Roosting and Nesting

Woodpeckers roost and nest in cavities. As evening falls, woodpeckers look for roosting cavities, either an old abandoned hole, or more frequently, a cavity they excavated specifically for roosting purposes. They excavate nesting holes at the start of the breeding season, usually in late April and May. Nesting and roosting cavities are usually only slightly larger then the width of the bird and are either round, rectangular, or gourd-shaped. Woodpeckers are very selective when choosing sites for their holes, tending to look for dead trees or snags that have a hard outer shell and a softer inner cavity. Some seem to find the soft cedar siding of many houses to be very useful for this purpose. Foraging

When foraging for insects, woodpeckers tend to excavate diseased, dying, or rotting trees. Woodpeckers are quite capable of drilling anything from tiny rows of holes to huge yawning craters into the wood of trees, utility poles, and even houses as they search for their meal.







Norther Flicker "anting" on the ground



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