Tri-National Migration Study
As of July, 2007, 56 ferruginous hawks have been captured and telemetered, eight in Mexico, eleven in Canada, and 37 in the United States. Ten juvenile hawks were captured and telemetered in 2007. The map to the right displays the current location, or last known location of the active study birds. Twenty-three telemetered hawks are currently active including three adults and four juveniles captured in previous years. Two juveniles and one adult telemetered last year died during the winter, and batteries expired on four other hawks.
The Ferruginous Hawk is an open-country raptor that nests in 3 Canadian Provinces, 17 states in the United States, and winters as far south as central Mexico (Bechard and Schmutz 1995). The largest nesting populations are in southern Alberta (1,181-2,223 nesting pairs) and Wyoming (>800 pairs) (Olendorff 1993). As much as 20% of the winter range of the species is in Mexico (Bechard and Schmutz 1995). Most northern populations of Ferruginous Hawks are completely migratory, whereas southern populations appear to migrate short distances or to be sedentary (Bechard and Schmutz 1995). Extensive banding studies across the northern part of the species range confirmed that breeding Ferruginous Hawks from Alberta, Saskatchewan, and North Dakota winter across the Great Plains to Mexico (Salt 1939, Gilmer et al. 1985, Schmutz and Fyfe 1987, Houston et al. 1998). Banding of Ferruginous Hawks west of the Continental Divide in Idaho (Thurow et al. 1980) and satellite telemetry of eleven individuals from Idaho and Utah suggested hawks from these areas moved widely throughout the west (Schueck et al. 1998).
An ongoing satellite telemetry investigation of the breeding population of Ferruginous Hawks in Washington state (Watson and Pierce 2000) has yielded considerable information on migration ecology: 1) Ferruginous Hawks migrate to many fall destinations (e.g., Canadian Provinces and Central Plains), followed by another major movement to winter ranges (e.g., California, Central Plains, and Mexico); 2) fall, winter, and breeding range fidelity is high; and 3) and that the continental divide is not a barrier to migration as has been proposed (Thurow et al. 1980, Gossett 1993).
Much remains to be learned about Ferruginous Hawk migration ecology throughout the extremes of this species range. A coordinated, international study is needed to provide an understanding of how regional ferruginous hawk populations interact throughout the year, and to better understand nesting and winter philopatry of regional populations. Information gained from this project will aid collective recovery and conservation goals for Ferruginous Hawks in Canada, the United States, and Mexico. The species is currently listed as endangered or threatened in several states, as Vulnerable in Canada, and is protected by the Migratory Bird Treaty Act (Bechard and Schmutz 1995). Identification of winter and breeding destinations from satellite telemetry will provide information on potential man-caused threats that may limit populations, and hawk survival.