The smallest and one of the most widespread of North American woodpeckers, the Downy Woodpecker is a year-round resident coast to coast and from the tree line in Canada and Alaska to southern Florida and the meager riparian forests of southern California. Audubon (Audubon and Chevalier 1840: 249) commented on its ubiquity and broad habitat tolerance:
"I have found it pretty generally distributed from the lower parts of Louisiana to Labrador, and as far to the westward as I have traveled. It seems, in fact, to accommodate itself to circumstances, and to live contented anywhere."
Although there is evidence of seasonal movements, these seem to involve only a small fraction of any population, are more likely dispersal than migration, and are not well understood. The Downy Woodpecker is equally at home in urban woodlots or wilderness forests and is readily attracted to backyard bird feeders. It is primarily insectivorous, focusing its foraging activities on surfaces, bark crevices, and shallow excavations of trees, shrubs, and woody weeds. Diet and foraging techniques vary with season and sex; indeed, this woodpecker has become a classic illustration of differential niche use by the sexes of a species: Males tend to forage more on smaller branches, females more on larger branches and trunks of trees.
The Downy Woodpecker varies geographically in size and plumage color and pattern, generally paralleling similar variation in the Hairy Woodpecker (Picoides villosus), although not as pronounced (Jackson 1970c, James 1970a, Ouellet 1977a). Sexes of adults are easily distinguished by the presence of a red nape bar in males; females lack this.
The Downy Woodpecker is a Linnaean species-named not by an American scientist, but by Carl Von Linne (= Linnaeus), the father of the science of taxonomy. Linnaeus, however, never saw a Downy Woodpecker, instead basing his description (Linnaeus 1758a) on the work of the American colonial naturalist Mark Catesby. It was Catesby who gave the bird its common name, with "Downy" a reference to the soft white feathers of the white stripe on the lower back, in contrast to the similar, but more hairlike feathers there on the Hairy Woodpecker (Wilson 1832). Various authors have suggested (incorrectly or less precisely) alternative meanings: Therres (Therres 1980) said simply that it was in reference to the soft appearance of its plumage; Jobling (Jobling 1991) suggested it was a reference to the lesser bristles covering the nostrils of the Downy as compared to those of the Hairy.
In some aspects, such as foraging ecology, the Downy Woodpecker is remarkably well studied. It has been the focus of several theses, dissertations, and major studies (e.g., Jackson 1970b; Smith 1971d; Quintana 1975; Bergstrom 1977; Ouellet 1977a; Stanek 1980; Sullivan Sullivan 1984c, Sullivan 1984c; Mecum 1994), although winter foraging ecology has received the greatest emphasis. Some aspects of its breeding biology have been studied in detail, but basic questions, such as whether pairs can raise more than one brood per year or what hatching and fledging rates are, have yet to be answered. Most detailed ecological studies have been in the northern and eastern United States (for example, Compton 1930, New York; Staebler 1949, Michigan). Two theses have focused on vocalizations and drumming behavior (Dodenhoff 1996, Mahan 1996) and there have been 3 major studies of geographic variation in the species (James 1970a, Ouellet 1977a, JAJ). A popular book (Ritchison 1999) on the Downy Woodpecker includes numerous excellent photos of nestlings and adults showing diverse behaviors and presents an overall review of the life history of this appealing species.