Meeting Abstract

3.5  Thursday, Jan. 3  Conditional Relationship between Bill Morphology and Vocal Performance in Lincoln’s Sparrows SOCKMAN, K.W.; Univ. of North Carolina, Chapel Hill kws@unc.edu

Individual variation in morphology can cause individual differences in behavioral performance. Although morphology affects behavior typically through a direct, physical link, in some instances the relationship may be indirectly mediated through a series of secondary mechanisms involving energetic or life-history factors. Through a direct, mechanical linkage, bill morphology governs maximal vocal performance in male songbirds. However, bill morphology may influence vocal performance through indirect mechanisms as well, such as one in which morphology influences foraging and the affordability of costly song. This raises the possibility that the relationship between bill morphology and vocal performance can vary with annual change in the environment. To investigate this prediction, I used an information theoretic approach to examine the relationship between several measures of vocal performance and bill morphology in Lincoln’s sparrows (Melospiza lincolnii ). I compared this relationship between two breeding seasons that differed markedly in environmental conditions, such as ambient temperatures, phenology of habitat maturation, and food abundance. I found a clear curvilinear relationship between bill shape (height/width) and song performance in the seemingly less hospitable season but not in the other season. Currently, I do not know the cause of the annual variation in this relationship. However, it could be due to the effects of bill shape on foraging and energetics that manifests only under difficult environmental conditions or, alternatively, to associations between male quality and both song performance and bill shape. Regardless of the cause, these results suggest the presence of an indirect, ecologically mediated link between bill morphology and vocal performance, the details of which are unknown.