Factors Affecting the Size of Ferruginous Hawk Home Ranges

We used radio-telemetry to track movements of seven adult male Ferruginous Hawks (Buteo regalis) in southcentral Washington. Home range size was estimated for each male using minimum convex polygon, harmonic mean, adaptive kernel, and fixed kernel-based methods. Minimum convex polygon and harmonic mean home ranges were significantly larger than those previously reported for Ferruginous Hawks. Home ranges varied substantially among males (mean = 90.3 km2, range = 17.7-136.4 km2). There was no relationship between home range size and brood size; however, there was a significant relationship (r2 = 0.964, P = 0.018) between home range size and the distance from the nest site to the nearest irrigated agricultural field where some males hunted. Kernel-based estimates showed two distinct core areas for most males, one around the nest and a second in the agricultural fields where they hunted.