Great Basin Naturalist


A nesting population of Ferruginous Hawks (Buteo regalis) at the eastern edge of the Great Basin in west-central Utah was studied for three nesting seasons, 1972–1974, during which time a significant decline in jackrabbit numbers occurred. The total number of hawks and nesting pairs varied throughout the study. In 1972, 16 pairs occupied territories and only 1 pair failed to nest. By 1974, however, only 5 pairs and 2 single birds occupied territories. The number of young fledged ranged from 31 in 1972 to 3 in 1974. The nesting phenology of the Ferruginous Hawk and the reproductive period of black-tailed jackrabbits are clearly correlated. Of the jackrabbit remains collected from hawk nests, 90 percent were from rabbits younger than 13 weeks. The decline in hawk numbers is thought to be directly correlated with a drop in the jackrabbit population.