Dappled black and white, like light filtering through the forest canopy onto a tree trunk, the Hairy Woodpecker is among the most widespread and familiar of North American birds. It is resident in forest and woodland habitats from near treeline in the far north and on mountains to the highlands of western Panama, many continental islands, and some islands of the Bahamas. In the Bahamas and some other areas, it is primarily a bird of the pines; but in many areas it is more catholic in its choice of forest habitats.
This woodpecker's name is derived from the long, filamentous white or whitish feathers in the middle of its back. Even among woodpeckers, it is particularly well adapted for climbing and pecking. Along with its smaller congener and look-alike, the Downy Woodpecker (Picoides pubescens), the Hairy is one of the best-known species of this group because it is easy to observe and comes readily to feeders. Away from feeders, it is relatively shy. The male has a narrow red patch or 2 smaller lateral patches of red on the back of the crown, readily visible in the field. The Hairy Woodpecker is larger than the Downy Woodpecker, has a heavier and longer bill, and usually lacks black markings on its outer tail feathers.
This woodpecker is one of the most geographically variable species among North American birds, displaying clinal patterns of variation in size and color across its range. Northern populations include the largest birds with the greatest proportion of white. In the western and southern parts of its range, white of the underparts can be replaced with light buffs, smoky grays, or smoky browns, and white of dorsal regions is reduced, sometimes considerably, or takes the color of the underparts. The Hairy Woodpecker is generally a resident species, although it can move locally in early fall. On calm, sunny days in late winter and spring, vocalizations and drumming can be heard for long distances. During the breeding season, it becomes so inconspicuous that its presence can go unnoticed, at least until eggs have hatched. When a few days old, young make their presence known in the nest cavity as they beg for food with loud, distinctive, raspy calls.
In spite of its wide range and familiarity to birders, this species has been the subject of few detailed studies, especially in recent years. Much of what is known is contained in hundreds of anecdotal notes and papers, with little major focus on the Hairy Woodpecker. More detailed studies include several of geographic variation, based on hundreds of specimens in collections (e.g., Jackson 1970c, Ouellet 1977a, Miller et al. 1999b); broad studies of behavioral ecology in Michigan (Staebler 1949) and Ontario (Lawrence 1967); studies of foraging behavior in New York (Kisiel 1972), New Hampshire (Kilham Kilham 1965, Kilham 1973b), California (Morrison and With 1987), and Quebec (Ouellet 1997); and of breeding biology in New York (Kingsbury 1932) and New Hampshire (Kilham Kilham 1966b, Kilham 1968a, Kilham 1969).