General Information

Citations:

• Goodrich, L.J., and J.P. Smith. 2008. Raptor migration in North America. Pp. 37-149 in K.L. Bildstein, J.P. Smith, E. Ruelas Inzunza, and R.R. Veit (eds.), State of North America's Birds of Prey. Nuttall Ornithological Club, Cambridge, MA, and American Ornithologists' Union, Washington, D.C
• Kennedy, P.L. (2003, January 2). Northern Goshawk (Accipiter gentiles atricapillus): a technical conservation assessment. USDA Forest Service, Rocky Mountain Region. Web. 01 August 2011: http://www.fs.fed.us/r2/projects/scp/assessments/northerngoshawk.pdf
• Lincoln, F.C. 1935. Migration of Birds. Circular 16, revision by J. Zimmerman (1998). U.S. Department of the Interior, U.S. Fish and Wildlife Service.
• Squires, John R. and Richard T. Reynolds. 1997. Northern Goshawk (Accipiter gentilis), The Birds of North America Online (A. Poole, Ed.). Ithaca: Cornell Lab of Ornithology; Retrieved from the Birds of North America Online: http://bna.birds.cornell.edu/bna/species/298
• Wheeler, B.K., C.M. White and J.M. Economidy. 2003. Raptors of Western North America: The Wheeler Guide.

Habitat Requirements

For habitat Northern Goshawks generally prefer mature or old-growth conifer, mixed hardwood-conifer, birch, or aspen forest for nesting. However, they have been found to also be generalists in terms of the types and ages of forests they can utilize, and can also found in younger forests intermingled with mature trees with high canopies for nesting (Goodrich and Smith 2008, p. 112; Kennedy 2003, p. 55). Sites near forest openings or edges for foraging also appear to be a preference for the Northern Goshawk (Goodrich and Smith 2008, p. 112).

Food Habits

The Northern Goshawk diet may vary depending on season and region, but generally consists of a combination of small rodents, squirrels (especially Richardson’s Ground Squirrels in the west), large songbirds and small to medium-sized game birds (Wheeler 2003, p. 197). The Northern Goshawk is primarily a perching and aerial forager, but Northern Goshawks often pursue prey on foot. Avian prey is also frequently caught on the ground or at low altitudes. Aerial pursuit may occur along a forest floor or in small woodland opening or woodland edges and over large open areas (Wheeler 2003, p. 197).

Movement / Home Range

The year-round range of the Northern Goshawk occurs in the majority of the western United States from Western Montana across to southeastern Montana and down to Arizona and New Mexico. The year-round range also covers the majority of the northeastern states from Pennsylvania north. Wintering areas are intermingled with year-round areas in the far western United States such as northern California and Washington, and cover most of the northern United States from western Montana across southern Minnesota and the Great Lakes region over into southern Pennsylvania, New Jersey, southern Connecticut and southeastern Massachusetts (Squires and Reynolds 1997). The Northern Goshawk is a short to medium distance migrant that flocks during migration. Migratory behavior is more common in the northern regions than southern regions and migrants often follow patterns of abundance of prey such as grouse and hares (Goodrich and Smith 2008, p. 112). The Northern Goshawk displays a variety of migration patterns including altitudinal migration. In contrast to other birds that begin fall migration as early as July, the Northern Goshawk does not begin migration until forced to do so by extreme winter weather or lack of food (Lincoln 1935, p. 16). Generally, fall migration appears to occur between August and November in the western states. Spring flights are less well documented and may be more dispersed (Goodrich and Smith 2008, p. 113).

Reproductive Strategy

Northern Goshawk pairs usually return to their nesting grounds around March or early April, with some returning as early as February. Some pairs have been observed to remain near their nests the entire year. Nests are typically constructed in the largest coniferous or deciduous trees available, and are constructed in the lower part of the tree. Eggs are produced in late April or early May with only one brood being produced per season. Clutch sizes usually range from around 2-4 eggs. Nestlings are semi-altricial when born and are usually ready for flight from the nest at around 35-36 days, with age of complete independence averaging around 70 days (Squires and Reynolds 1997).

Other

The primary threat to Northern Goshawk populations is thought to be loss of its preferred nesting habitat for purposes of timber harvest and through other types of habitat alteration. However, due to the lack of data on Northern Goshawk populations, the degree of the effect of habitat modification on the Northern Goshawk is unknown (Kennedy 2003, p. 8).