Introduction

The Gila Woodpecker is a noisy, aggressive species that is characteristic of arid habitats in a limited part of the southwestern United States and northwestern Mexico, being most abundant on the desert mesas of southern Arizona. It is characteristic of sparsely covered deserts containing large saguaro cacti (Carnegiea gigantea), but the bird’s range extends farther north, east, and west than that of the saguaro.

The species is largely sedentary, with some movement to the north or to higher elevations in winter. While often closely associated with saguaros, the Gila Woodpecker also makes ready use of riparian woodlands and residential areas. It is an omnivore, eating flowers and fruits of saguaros and other cacti and plants, insects, other animals, and even bird eggs.

The woodpecker has interesting associations with other species. It acts aggressively toward numerous species, and at the same time provides cavities for many secondary cavity-nesters. European Starlings (Sturnus vulgaris) compete directly with Gila Woodpeckers for nest cavities and pose a potential threat to some populations.

Coverage of the species’ life history is uneven: Some aspects have been studied extensively and others have been left virtually untouched. Particularly important contributions include those on general life history (Bent 1939), systematics (Selander and Giller 1963), foraging (Rosenberg et al. 1982, Martindale 1983), physiology (Braun 1969), vocalizations (Brenowitz 1978a, 1978b), nesting characteristics (Gilman 1915, Soule 1964, Inouye et al. 1981, Kerpez and Smith 1990b), populations and effects of human activity (Emlen 1974, Anderson et al. 1982, Tweit and Tweit 1986, Rosenberg et al. 1982, 1991, Kerpez and Smith 1990a), molts and plumages (Ridgway 1914, Selander and Giller 1963, Pyle and Howell 1995, Pyle 1997), and morphological measurements (Martindale and Lamm 1984).