Integrated plumage colour variation in relation to body condition, reproductive investment and laying date in the collared flycatcher

White plumage color as an honest indicator: feather macrostructure links reflectance with reproductive effort and success

Abstract

The structural condition of feathers may generally have a decisive role in shaping the color properties of the plumage. However, the information content of structurally mediated color differences is poorly known. This makes it particularly hard to determine the meaning of color variation in pigment-free white plumage patches. The white wing patch of the collared flycatcher (Ficedula albicollis) is an important sexual trait, and changes in its reflectance are partly due to macrostructural condition. We used 2 years of macrostructural, reflectance, and breeding data from both sexes to examine whether wing patch macrostructure lends information content to actual reflectance in terms of reproductive effort and success. Macrostructure strongly predicted actual reflectance in males but only weakly in females. Furthermore, in males, feather vane width was related positively to current year reproductive effort, and negatively to previous year reproductive effort. This indicates that macrostructurally mediated reflectance attributes may inform the receiver not only of actual reproductive capacity but also of individual quality via reproductive costs.

Significance statement

Coloration of animals takes a central place in their communication and in advertising reproductive abilities. Although white plumage is widespread among animals, usually we have little knowledge on how its structure is linked to reproduction. We investigated this link in a wild population of collared flycatchers. We demonstrated that white feather structure was related to coloration and with current year and previous year reproductive capabilities in males. Our results suggest that white feather structure has the potential to connect reproductive costs with coloration.

Female and male plumage color is linked to parental quality, pairing, and extrapair mating in a tropical passerine

Sexual selection has been proposed to drive the evolution of elaborate phenotypic traits in males, which often confer success in competition or mating. However, in many species, both males and females display such traits. Studies examining how selection acts on both sexes are scarce. In this study, we investigated whether plumage ornamentation is sexually selected in females and males lovely fairy-wren Malurus amabilis, a cooperatively breeding songbird. We found that female and male plumage color was correlated with parental quality but not with individual quality or survival. We also found evidence of positive assortative mating based on plumage color. Microsatellite analyses of paternity indicated that the lovely fairy-wren has high levels of extrapair paternity (EPP), with 53% of offspring (in 58% of broods of 57% of females) resulting from extrapair (EP) mating. Female and male plumage color did not predict reproductive success or the proportion of EP offspring in their own nest, but less colorful males obtained higher EPP when paired with more colorful females and gained overall higher total paternity (own nest and other nests). We argue that plumage color may be under sex-specific selection, highlighting the importance of looking at both sexes in studies of sexual selection and ornament evolution. The current findings together with the previous study suggest that plumage color in female and male lovely fairy-wrens appears to be an honest signal relevant in both intrasexual and intersexual competition contexts.