Meeting Abstract
35.2 Friday, Jan. 4 When biomechanics meets biogeochemistry: functional correlates of Loggerhead Shrike (Passeriformes: Laniidae) feeding ecology based on stable isotopes analysis SUSTAITA, D*; RUBEGA, M; HARTMAN, G; University of Connecticut, Dept. of Ecol. and Evol. Biology; University of Connecticut, Dept. of Ecol. and Evol. Biology; University of Connecticut, Dept. of Anthropology diego.sustaita@uconn.edu
Loggerhead Shrikes are medium-sized (~50 g) passerines that feed on arthropods and vertebrates. Differences in the physical and behavioral attributes of their prey are likely to impose disparate demands on their beaks and jaws. For instance, capturing and dispatching vertebrate prey may select for greater length and curvature of the bill hook, as well as greater bite force capabilities. These features, however, might trade-off against one another, because longer hooked tips may be more susceptible to fracture under greater loads. Previously, we reported a significant negative relationship between a bill shape characterized by increasing hook tip length and curvature, and bite force, in a wild population of Loggerhead Shrikes. Furthermore, we found that bite pressure (force/area) is unrelated to bill tip shape, suggesting that, across individuals and populations, shrikes of different bill tip shapes can achieve functional equivalence in terms of force/area by modulating bite force. Here we use analysis of carbon (d13C) and nitrogen (d15N) stable isotopes of feathers and prey items to place shrike morphology and performance in the context of their feeding ecology. Upper bill shape variables are uncorrelated with isotopic values, but bite performance is negatively related to d13C and quadratically related to d15N. It is as yet unclear specifically how these isotope values relate to prey use, however these results suggest that bite performance might not only mitigate the effects of variation in bill tip shape, but might also mediate the relationship between bill morphology and a dynamically changing prey base.
