Breeding Habitat:Grassland
Nest Type:N/A
Migration Status:Short distance migrant
Nest Location:N/A
The Ferruginous Hawk is an uncommon and locally distributed occupant of grasslands, sagebrush, and desert scrub habitats in the Great Plains and Great Basin regions. On the Great Plains, breeding pairs are normally associated with native grasslands (Gilmer and Stewart 1983). In the Great Basin, they are normally found in habitats that have not been greatly disturbed by grazing or other agricultural activities (Harlow and Bloom 1989).
Ferruginous Hawk populations have undergone noticeable declines in recent decades. These declines are most evident in the Prairie Provinces of Canada (Houston and Bechard 1984, Schmutz 1984) and in the western United States (Harlow and Bloom 1989). Historically, Ferruginous Hawks experienced declines in the southwestern states, although recent trends are uncertain (Hall et al. 1988). Habitat destruction, reduced prey availability, and persecution have been implicated in these declines (Harlow and Bloom 1989).
As is true for many raptors, Ferruginous Hawks tend to be poorly represented along BBS routes. They are recorded in small numbers throughout their range (Relative Abundance Map). They are also generally recorded in small numbers on CBCs.
While this species may have experienced some declines in recent decades, the BBS trend data for Ferruginous Hawks tend to be fairly positive. The survey-wide indices show an increasing tendency, especially after 1980 (Survey-wide Annual Indices). Increasing populations prevail throughout most of their range (Trend Map). The 1966-1979 trend estimates are generally produced from very small samples, and these trends are non-significant (Trend List). After 1980, significant increases are indicated for Colorado and Montana, and the High Plains (S36) and Great Plains Roughlands (S39) strata that include portions of these two states. The increases in these two states are responsible for similar trends in the Central BBS Region, United States, and the survey-wide population. These recent increases are evident in the indices for both states (Colorado Annual Indices) (Montana Annual Indices). Trends in the Great Basin states tend to be stable (Utah Annual Indices). The significant increases during 1980-1994 are responsible for similar trend estimates over the entire survey period.
Local population increases by this species are not unexpected, since it is known to be fairly nomadic and local influxes have been documented in response to prey availability (Gilmer and Stewart 1983). The fact that population increases in Colorado and Montana are largely responsible for the regional and survey-wide trend estimates indicates that the latter estimates should be viewed with great caution, especially if they are contradicted by results from other studies. While some Ferruginous Hawk populations may have increased during the late 1980s (Harlow and Bloom 1989), there are no published accounts describing their trends subsequently. Until regional increases are documented from other data, the potential inaccuracies in the regional BBS trend estimates for this species should be recognized. However, it is important to note that trend estimates based on CBC data are entirely in a positive direction, with significant increases indicated for most states. These data provide some support for the positive trends recorded by the BBS.
Gilmer, D.S., and R.E. Stewart. 1983. Ferruginous Hawk
populations and habitat use in North Dakota. Jour. Wildl.
Manage. 47:146-157.
Hall, R.S., R.L. Glinski, D.H. Ellis, J.M. Ramakka, and D.L. Base.
1988. Ferruginous Hawk. Pp. 111-118 in R.L. Glinski et al.,
eds. Proceedings of the southwest raptor management symposium
and workshop. Natl. Wildl. Fed. Scien. Tech. Ser. No. 11.
Harlow, D.L., and P.H. Bloom. 1989. Buteos and the Golden Eagle.
Pp. 102-110 in B.G. Pendleton, ed. Proceedings of the
western raptor management symposium and workshop. Natl.
Wildl. Fed. Scien. Tech. Ser. No. 12.
Houston, C.S., and M.J. Bechard. 1984. Decline of the Ferruginous
Hawk in Saskatchewan. Am. Birds 36:166-170.
Schmutz, J.K. 1984. Ferruginous and Swainson's hawk abundance and
distribution in relation to land use in southeastern Alberta.
Jour. Wildl. Manage. 48:1180-1187.