What's with hue? An exploration of sexual dichromatism in chipping sparrows

Abstract

In some species of birds male and female plumage reflects differently in the UV spectrum. This “hidden” (to the human eye) form of sexual dichromatism has been uncovered through advances in reflectance spectrometry. We were interested in crown color as a potentially UV dichromatic sexually selected trait in chipping sparrows. We studied sexual dichromatism in the UV and visible spectrums, as well as correlations between crown color and morphology. In our study sample of live birds and dead museum specimens there was no statistically significant difference between males and females in the UV or visible spectrums, however there was a trend towards dichromatism in UV hue. We also found a significant correlation between male wing length and UV hue as well as a significant degree of sexual dimorphism in wing length. Previous studies relating dimorphism in wing length to sexual dichromatism may support the trend in sexual dichromatism.