CORVIDAE, E. L.; BIERREGAARD, R. O.; PETERS, S. E.*; Univ. of North Carolina, Charlotte: Comparison of wing muscle morphology in three raptors

Red-tailed hawks (RTHA), Cooper�s hawks (COHA) and Ospreys (OSPR), differ in their typical flight patterns: RTHA�s use a broad soaring wing to glide over fields searching for prey; COHA�s elliptical wing reflects its woodland foraging, pursing small birds into dense undergrowth; OSPRs soar, but also hover over water, dive and must take-off carrying the fish. Using undamaged carcasses, we compared 12 forelimb muscles between species to examine biomechanical factors related to these differences in locomotor behavior. Muscle force was estimated from average cross-sectional areas, and relative oxidative/glycolytic capacity was measured using activity levels of citrate synthase (CS) and lactate dehydrogenase (LDH). OSPR had significantly greater cross-sectional area than the other two birds in wing depressors, flexors, patagial tensors, dorsal and ventral rotators, elevator, and pronators. Only forearm supinators and wing retractors were equally large in RTHAs. COHAs had signficantly less cross-sectional area than the other two birds except in the pectoralis and the wing flexors, where no difference was found between them and RTHAs. Preliminary results of enzyme assays suggest COHAs are the most metabolically diverse: in the pronators, supinators and depressors, they had both the highest levels of CS and of LDH. OSPR had highest levels of both CS and LDH in the wing retractors and patagial tensors. The correspondance of high CS and LDH in the same muscles suggests that they are composed predominantly of fast, oxidative/glycolytic muscle fibers. These results are consistent with the high degree of wing rotation (pronation/supination) found in COHAs for maneuvering. As relatively large birds, OSPR must exert large forces in both hovering and rising from the water. This is consistent with our force estimates.