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Researchers tracked ferruginous hawks in southwest Idaho and found that their movements responded predictably to seasonal variation but unexpectedly to human modifications to the landscape.

Variation in the home range size of animals can be driven by many factors including availability of food, nesting sites, and perching sites. In some cases, human influences can change where these resources are located on the landscape and alter behavior. Researchers tracked the movements of 12 ferruginous hawks in the Morley Nelson Snake River Birds of Prey National Conservation Area—or NCA--in southwest Idaho. The NCA contains nesting platforms and irrigated cropland with high densities of rodent prey. The results confirmed expected patterns: adults had smaller ranges close to their nest sites during breeding season compared to the rest of the year. Juveniles had larger ranges year-round and more nomadic behavior. One interesting pattern was observed: during the nesting season, use of cropland was associated with larger home ranges, but during the non-breeding season use of cropland was associated with smaller home ranges. This could be a result of hawks using nesting platforms that are far from foraging sites during the breeding season, while during the non-breeding season birds are not tied to a nest platform. These results provide important insights into how human modifications to the landscape, in this case nesting platforms and cropland, can influence wildlife movements.  

Isted, G., Thomas, R.J., Warner, K.S., Stuber, M.J., Ellsworth, E.A., and Katzner, T.E., 2023, Ferruginous Hawk movements respond predictably to seasonal variation but unexpectedly to anthropogenic subsidy: Ibis, Online. 


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