Male viability is positively related to multiple male ornaments in Asian Barn Swallows

Abstract

The European Barn Swallow Hirundo rustica rustica is a model system for studying female mate choice for indirect benefits, as the long tail of males, the target of female mate choice, is positively related to male viability. However, situations may differ in other subspecies where male ornaments other than tail length are prominent and seem to be the targets of female choice. In this study, similar to previous studies on European populations, we determined the relationship between male viability and male ornaments, including tail length, in a Japanese population of the Asian Barn Swallow H. r. gutturalis, which have short tails, a whitish ventral plumage, and a large red throat patch. We observed that males with longer tails and larger and more colored (i.e., lower saturation values) throat patches were more likely to return to the study area than other males, independent of their age. Of these ornaments, information on viability of male tail length partially overlapped the information on viability by throat coloration. Because females choose mates, either directly or indirectly, based on their throat coloration, female mate preference for tail length had few benefits for the choosers. This may explain why female mate preference for tail length was not observed in this population. In addition, differing from a previous study in a European population, male throat patch size may serve as a good indicator of male viability, independent of tail length and throat coloration in this population. We discuss the possible explanations for the observed patterns.