Nesting Behavior, Provisioning Rates, and Parental Roles of Ferruginous Hawks in New Mexico

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A better understanding of feeding ecology and parental roles is important for conservation of Ferruginous Hawks (Buteo regalis) and their habitat. In 2004–2005, we collected and analyzed 1373 hr of video from six time-lapse video-monitored nests in New Mexico, U.S.A., to address these behavioral data gaps. Ferruginous Hawks delivered 93 g of prey biomass per hr to each nest (g/hr), 42 g/nestling/hr, and 208 g/prey delivery. Males delivered most prey items (72%) and twice the overall prey biomass of females, but females delivered larger prey items in each delivery. As predicted by the food-niche hypothesis, males and females used prey differently, with females delivering a disproportionate number of desert cottontails (Sylvilagus audubonii) and males delivering Botta’s pocket gopher (Thomomys bottae) most often. Desert cottontails, the heaviest prey item, were most often delivered eviscerated. Females spent 33% of recorded time at the nest, whereas males spent ,1%. We found a positive relationship between female nest attendance and male provisioning rate, and a negative relationship between female nest attendance and nestling age; the role of the male was to deliver prey whereas the female’s initial role was to feed and care for nestlings, then to find food as nestlings began feeding themselves and became homeothermic. Evidence of intersexual differences in prey use may provide managers justification to focus limited resources on actions that create habitat heterogeneity and, consequently, a more diverse prey base.