Woodpecker - biology.

Woodpecker - biology. Woodpecker, nonsinging bird known for its habit of hammering on trees with its bill. Woodpeckers vary in size from 15 to 53 cm (6 to 21 in). There are about 210 species, found throughout the world except in Australia, New Zealand, and most of the Pacific Islands. Most woodpeckers live in South America and southeastern Asia. Woodpeckers are known for their ability to cling to the trunks of trees and dig holes in the wood with their beaks. A woodpecker's first and fourth toes are directed backward, and its second and third are directed forward. (In a few species, one of the two rear toes has been lost.) This foot, with its sharp claws, enables the bird to go up and down tree trunks. Except in the piculets and the wrynecks (see Wryneck), the woodpecker's tail is stiffened, with the shafts of the feathers terminating in hard spines, which the birds press against a vertical surface to help support their weight. The tail serves as a prop against a tree and also helps the woodpecker go up and down tree trunks. Other characteristics are the straight, hard bill, with the nostrils covered by fine, wiry feathers; a powerful neck for hammering; and a remarkably long tongue, either sticky or barbed, which is used to ensnare insects hidden in crevices. Woodpeckers may be brightly colored in combinations of all hues except blues or violets. Almost without exception, the male has an area of bright yellow or red somewhere about the head. Woodpeckers nest anywhere there are trees, from rain forests to city parks. They are usually solitary in habit. Woodpeckers nest in holes in trees, which they usually excavate. All females lay white eggs on a bed of wood chips and sawdust at the bottom of the nest. Their voices are harsh and shrill; during the breeding season many beat a tattoo on a hollow limb as a substitute for a song. The birds subsist mainly on insects, which they detect by tapping the wood of trees with their bills. They excavate the insects with pickaxlike strokes of the bill. Since woodpeckers feed almost entirely on insects and the eggs and pupae of insects, they are of great importance in helping preserve the world's forests. The most familiar woodpeckers in much of North America and Eurasia are rather small, black-and-white species. The downy woodpecker is common not only in woodlands but also in orchards and in shade trees of residential areas of cities. The larger hairy woodpecker is almost identical in color, but is less often seen outside forests. The acorn woodpecker, found from Oregon to Colombia, is remarkable for its habit of drilling a series of holes in tree trunks in which to store acorns for future use. Still common in the United States and Canada is the crow-size pileated woodpecker, which is up to 49 cm (19.5 in) long. It is black, with a red crest, a white line down the long neck, and a white flash in the wings. The red-headed woodpecker is familiar throughout most of the world. It is robin-size with an all-red head. The back, shoulders, wingtips, and tail are black with white patches on the rump and wings, and white underparts. The red-bellied woodpecker is a robin-size species with a zebra-striped back and entirely red crown. The underparts are whitish, and some males have a red wash on the belly. It inhabits woodlands from the Great Lakes to the Gulf of Mexico. The gila woodpecker is similar to the red-bellied, but the crown has only a patch of red. It is the only species of this coloration that is found in the desert brushlands of the West and Southwest. The largest species, the imperial woodpecker of the Sierra Madre Occidental of Mexico, is probably extinct. It was about 53 cm (about 21 in) long, with a long neck and long crest. Closely similar and only slightly smaller, the ivory-billed woodpecker may also be extinct. It had been found throughout the southeastern United States and eastern Cuba, but had not been seen for many years. In 2005 scientists reported in Science magazine that an ivory-billed woodpecker had been sighted in 2004 in the Cache River National Wildlife Refuge in Arkansas. Previous sightings of the bird in the United States had been rare, and none had been confirmed by ornithologists (scientists who study birds). The scientists based their finding on a videotape of the bird, sound recordings, and the accumulated evidence of sightings. In 2006, however, Science magazine revisited the issue by publishing two reports, one disputing the 2005 report and the other supporting it. Ornithologist David A. Sibley and two of his colleagues argued that the videotape shows a pileated woodpecker, which has white patches on the bottom of its wings. In rebuttal John W. Fitzpatrick, director of Cornell University's Lab of Ornithology, countered that the blurry white patches captured in the video are on the top of the wings, which would make it an ivory-billed woodpecker. Scientific classification: Woodpeckers make up the family Picidae of the order Piciformes. The red-headed woodpecker is classified as Melanerpes erythrocephalus. The red-bellied woodpecker is classified as Melanerpes carolinus. The imperial woodpecker is classified as Campephilus imperialis, the ivory-billed woodpecker as Campephilus principalis, and the pileated woodpecker as Dryocopus pileatus. The familiar black-and-white species of Eurasia belongs to the genus Dendrocopos, those of North America to the genus Picoides. The downy woodpecker is classified as Picoides pubescens, the hairy woodpecker as Picoides villosus, and the acorn woodpecker as Melanerpes formicivorus. The gila woodpecker is classified as Melanerpes uropygialis. See also Flicker; Sapsucker. 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