Achromatic plumage reflectance predicts reproductive success in male black-capped chickadees

The size of achromatic (black, white, gray) plumage patchesserves as a male status signal in many species of birds, butvariation in the colors of these patches has received littleattention. We assessed the relation between achromatic plumagereflectance, dominance rank, body condition, and reproductivesuccess in male black-capped chickadees, Poecile atricapillus.We measured plumage reflectance for five body regions of 40male chickadees in late winter and monitored these males throughoutthe following breeding season to determine whether they survivedto breed, whether they successfully paired, whether their partnerlaid eggs, and both their apparent and realized reproductivesuccess. As expected from past studies, a male's dominance ranksignificantly predicted whether his partner laid eggs. However,only achromatic plumage reflectance significantly predictedother measures of male reproductive performance. Among maleswho fledged at least one offspring, both the brightness of whiteplumage regions and the UV-chroma of melanin-based plumage regionswere significant predictors of the proportion of within-pairyoung in their nests. When we consider all males we measured,assigning zero values to males who failed to sire any offspring,the UV-chroma of melanin-based plumage regions was a significantpredictor of realized reproductive success. Bib size was alsorelated to male realized reproductive success. Our findingssuggest that individual variation in achromatic plumage mayplay an important role in sexual signaling in chickadees.