Movements of Ferruginous Hawks from the Intermountain West
The ferruginous hawk (Buteo regalis) is found in grasslands and sagebrush habitats in western North America. It is listed as a sensitive species or species of concern throughout much of the western United States. It is considered a short-distance migrant and partial migrant – those in the northern latitudes migrate whereas those in the southern latitudes apparently don’t travel far. In certain areas adults do not regularly return to breed. Our goal was to describe the annual range and landscape use of this species. We tracked 15 ferruginous hawks via satellite-received Platform Transmitter Terminal (ID=6, UT=5, NV=4) in studies supported by the Department of Defense Legacy Resource Management Program, the Bureau of Land Management, and the Nevada Department of Wildlife.
Ferruginous hawks that nested in southwestern Idaho and north-central Utah traveled extensively throughout the west before going to winter areas. Movement patterns were highly variable among individuals. Likewise, winter areas varied among individuals but tended to be south and west of their nesting areas. Although ferruginous hawks “toured” regions in the west before going to winter areas, routes back to nesting areas were comparatively direct.
It is possible that “nomadic” movements decrease adult mortality when an individual travels to better foraging areas when prey availability declines in a previously used area. Furthermore, ferruginous hawks live as long as 20 years. As nomadic predators, they might “ track” spatially and temporarily variable prey abundance to best exploit prey populations across a broad breeding area. Perhaps after a nesting failure in one year, they relocate to an area that is potentially more suitable in a subsequent year(s). This might be particularly advantageous to ferruginous hawks favoring prey that cycle in abundance (e.g., some ground squirrels and hares).