Melanin-based coloration reflects alternative strategies to cope with food limitation in pigeons

Variation in genetic-based coloration is widespread among vertebrates, yet the underlying mechanisms explaining this polymorphism maintenance remain poorly known. Gene-by-environment interactions on fitness traits in a fluctuating environment are often invoked to explain the maintenance of such color diversity. According to this hypothesis, variation in coloration could signal alternative life-history strategies to cope with variable environmental conditions. However, empirical studies testing this hypothesis are still rare. Here, we aimed at comparing the variation of body mass maintenance behavior and reproductive traits between differently colored individuals in alternative environments. We exposed differently colored captive feral pigeons to different food conditions and immune challenges and measured their investment in body mass maintenance, egg laying, and offspring quality. Under food restriction, darker eumelanic females had a higher egg production, but darker adults tended to lose more body mass than paler conspecifics. Moreover, offspring reared in food-limited conditions had a higher body mass at fledging when sired by darker biological fathers, suggesting a positive genetic effect of a darker eumelanic coloration in harsh food conditions. In contrast, when food was abundant, pale- and dark-colored females had a similar egg production, but darker adults lost significantly less body mass than paler conspecifics. The immune challenge had no effect on adult body mass maintenance and reproduction. Differently colored individuals may thus display alternative reaction norms to different food conditions, suggesting that eumelanin-based coloration reflects how animals cope with variations in food availability. Spatiotemporal heterogeneity of food availability in natural systems may thus play a central role in the evolution of melanin-based coloration in wild animal populations.