The relationships between winter climate and selection on body size of house sparrows

Publisher Website
Google Scholar
Abstract
Overwinter modification of the morphology of house sparrows was examined in relation to the intensity of proximate wintertime climatic conditions. Samples were a posteriori for 4 of 6 comparisons for males and 3 of 5 for females. Two comparisons were collected specifically (1 recently) to examine overwinter changes. Comparisons were of multivariate assessments of skeletal measurements for subadult (males only) and total fall vs. total spring samples. There were significant differences in PC1 (overall body size) between fall and spring groups for 3 of 11 comparisons. For males, the overwinter change in size was significantly correlated (P < 0.01) with the proximate level of precipitation. For females, overwinter change in size correlated best with the deviation of a winter''s temperature from the all-time mean winter temperature (P < 0.05). Only for females did changes in variance correlate with climate (temperature deviation, P < 0.05). Increasing severity of winter climate may result in larger males, but smaller (and less variable) females. A combination of physiological (energetic), behavioral (dominance relations) and ecological pressures may cause the observed size changes.