The Cooper's Hawk is a crow-sized woodland raptor that breeds throughout much of the United States, southern Canada, and northern Mexico. Despite its broad distribution, it is a secretive, inconspicuous species, particularly in the breeding season and even in areas where it is a common nester. It is more readily observed as a bird of passage at well-known migration watchsites, locations where raptors concentrate in migration. Female Cooper's Hawks are about one-third larger than males, and indeed this species shows among the greatest reversed size dimorphism of any of the world's hawks. Vocalizations, especially by the female, may be an essential element of the pair bond in this highly dimorphic bird. Midway in size between North America's larger Northern Goshawk (Accipiter gentilis) and the smaller Sharp-shinned Hawk (A. striatus), the Cooper's Hawk, like these other Accipiters, is a quintessential woodland hawk. With short, powerful, rounded wings and a relatively long tail that ensures maneuverability in dense cover, it is well adapted for quick pursuit of forest birds and mammals.
The Cooper's Hawk breeds in extensive forests and smaller woodlots of deciduous, coniferous, and mixed pine-hardwoods, as well as in pine plantations, in both suburban and urban habitats. It captures a variety of prey, mainly medium-sized birds and mammals such as doves, jays, robins, chipmunks, and other rodents.
Some eastern populations declined significantly in the mid-1900s, owing to shooting, trapping, and pesticide contamination. Although Cooper's Hawks are still designated as Threatened or Endangered in several eastern states, evidence suggests that breeding populations have recovered in many areas.
The species was named in 1828 by Charles Bonaparte (American Ornithology) for his friend and fellow ornithologist, William C. Cooper, a New York scientist and father of James C. Cooper, who was later honored in the title of the Cooper Ornithological Society ( Mearns and Mearns 1992a ).
Population trends generated from migration count data are available from Hawk Mountain Sanctuary and Cape May (see Table 1 , also see Bolgiano 1997 for CBC in Pennsylvania). McConnell ( Mcconnell 2003 ) gives a good summary of recent changes in the species' distribution and abundance. Over the past decade, there have been concerted efforts to document the species' habitat preferences in various parts of its range, with some emphasis on differences in quality of nesting habitat quality (measured by density and productivity) in natural vs. human-altered landscapes (e.g. suburbia, plantations). Studies of this type have occurred in Arizona ( Boal and Mannan 1999 , Boal and Mannan 2000 ) and Wisconsin ( Rosenfield et al. 2000a ). Information on nest-site selection is available for New Jersey and New York ( Bosakowski et al. 1992a ), New Mexico ( Siders and Kennedy 1994 ), Arizona ( Boal and Mannan 1998 ), Wisconsin ( Trexel et al. 1999 ), Pennsylvania ( Mcconnell 2003 ) and North Dakota ( Nenneman et al. 2003 ). One long-term study in Wisconsin has described nesting chronology, productivity, habitats and density ( Bielefeldt et al. 1998 ).