The Attack and Strike of Some North American Raptors

QUALITATIVE observations of the attack and strike of raptorial birds are numerous, but few quantitative measurements are available of the velocity, descent, acceleration, and deceleration of the pelvis, legs, and feet. My anatomical studies of the adaptations of the pelvic limb of selected species of North American birds of prey (MS) led to the present study because an understanding of how raptors use their feet and legs during the attack and strike facilitates the interpretation of anatomical differences. I used cinematography as a means of recording these data accurately (Hildebrand, 1963, 1964). The data presented here are somewhat limited. As the prey species were loosely tethered to the ground or a piece of canvas some distance from the raptor, the prey situations presented to the predator were not so varied nor were the prey so active as those normally encountered. Secondly although some variety of prey species was used, it was not possible to present each hawk or falcon with many different kinds. A given species of raptor captures a diversity of prey: Beebe (1960) and Storer (1966) indicate that the accipters and falcons are opportunists, preying upon those animals available and most easily secured. Possibly hawks and falcons attack and strike larger prey in a different manner than they do smaller ones. Lastly, an individual bird may employ a variety of hunting, attacking, and s.triking attitudes not characteristic for its particular species (Cade, 1960; White, 1962; Mead, 1963).