SUSTAITA, Diego; HERTEL, Fritz; California State University, Northridge; California State University, Northridge: Myology and biomechanics of the hindlimb and jaw of North American hawks and falcons in relation to bite and grip force

Previous studies have indicated that differences in hindlimb and beak characteristics among raptors reflect differences in predatory mode and prey habits. Falcons kill primarily with their beaks, whereas most hawks kill with their feet, and it has been demonstrated that bird-eating raptors tend to have shorter, wider, deeper beaks and longer toes, in comparison with those that feed predominantly on mammalian prey. This study expands upon these findings by focusing on the myology and biomechanics of the hindlimb and jaw apparatus of North American hawks and falcons. Hawks are predicted to have stronger feet than falcons, which in turn are predicted to possess stronger jaws. Moreover, within groups, those with a greater propensity for mammalian prey are predicted to have comparatively stronger jaws and feet. Force estimates were derived from measurements of physiological cross-sectional area and indices of mechanical advantage for the major jaw adductors and digit flexors. Preliminary results suggest that differences in killing behavior are reflected in jaw and hindlimb musculo-skeletal characteristics. For instance, the jaw musculature of falcons comprises a slightly greater proportion of total (hindlimb and jaw) muscle physiological cross-sectional area compared with that of hawks, whereas the hindlimb musculature of hawks comprises a slightly greater proportion than in falcons. The ultimate objective of this study is to elucidate the adaptive functional significance of musculo-skeletal characters as predictors of predatory capability and foraging ecology of these raptors.