Inter-annual variation and information content of melanin-based coloration in female Eurasian kestrels

Competition for resources (e.g. mates or food) is the main evolutionary explanation for conspicuous ornaments in males, although this idea is not generalized in females. Whether or not the expression of melanic coloration is dependent on environmental conditions remains controversial. We studied three different melanin-based female traits in the Eurasian kestrel Falco tinnunculus , a sexually dichromatic species, for a period of 10 years: grey coloration in rump and tail and the width of the black subterminal tail band. We analysed these traits for within-individual variation among years, as well as their possible link with indices of quality, such as age, body size, and breeding performance. The results obtained demonstrate that female melanin-based coloration increased from yearlings to adults. In addition, the expression of female rump coloration covaried positively with the environmental conditions in the previous year (i.e. measured as clutch size at population level). Finally, we found a positive correlation between grey rump coloration and clutch size. These results suggest that the expression of rump coloration, a melanin-based trait, is environmentally constrained, and we propose that this character could function as an indicator of individual quality in female Eurasian kestrels.  © 2009 The Linnean Society of London, Biological Journal of the Linnean Society , 2009, 97 , 781–790.