Ecomorphological Indicators of Feeding Behavior in Recent and Fossil Raptors

Modern raptors feed predominantly on animals and exhibit a wide range of feeding behaviors and prey preferences. The following six ecomorphs, based on feeding preferences served to classify members from all families of diurnal birds of prey: (1) avivores, which feed primarily on avian prey; (2) mammalivores, which feed primarily on mammalian prey; (3) herpetivores, which feed primarily on reptiles and amphibians; (4) piscivores, which feed primarily on fishes; (5) scavengers, which are primarily carrion feeders; and (6) generalists, which are opportunistic feeders on all of the above prey and on invertebrates. A series of skull-based indices were created to reflect functional aspects of prey preferences-calculated from measures of the cranium, maxilla (beak) and mandible-and were analyzed separately and with all units combined. The same indices were determined for 13 raptor species, including some extinct genera unearthed from the Pleistocene Rancho La Brea tar pits in California. A discriminant function analysis was used to assess the functional predictability of the indices for the extant raptors and also to predict the ecomorphs of the fossils. Results indicate that all of the indices combined provide the best predictor of prey preferences, especially for scavengers and avivores. Cranial and mandibular indices provide a better resolution than maxillary indices when considering only isolated elements. Eleven fossil species were assigned to their dietary categories with high probabilities and two were less definitely classified.