CORBIN, C.E.; Bloomsburg Univ. of Pennsylvania: Attack rates, morphology and phylogeny in sit-and-wait passerine birds

Usually, bird species are lumped as either sit-and-wait or active foragers. In addition, morphology is hypothesized to predict foraging mode membership. At broad phylogenetic scales (e.g. Passeriformes), the morphology-ecology relationship is clear. Relative to overall body size, sit-and-wait foragers have short legs and wide catch-all bills, while active foragers tend to have relatively longer legs and tweezer-shaped, precision bills. Within a foraging mode, are ecomorphological relationships fine-tuned enough to reflect the large scale trends? Attack rate is the mean number of times per second a bird attempts to capture a prey item; hence, it is a metric of the relative amount of sit-and-wait versus active foraging of a bird. I tested for a relationship between attack rate and morphology in a polyphyletic grouping of sit-and-wait foraging passerine bird species. Species were from two regions in North America, one region in Central America and two regions in eastern and southern Africa. I used principal components on morphology and regression analyses to test for a relationship among the species. There was a significant negative relationship between attack rate and overall body size but not with allometric aspects of body shape. This pattern may be explained by energetics but the lack of an allometric morphological relationship with attack rates is counter to what one would expect from ecomorphological predictions. In addition, after accounting for phylogeny, the body size�attack rate relationship holds for certain subgroups but these patterns may not be universal to sit-and-wait passerines in general.