Mating advantage of multiple male ornaments in the Barn Swallow Hirundo rustica gutturalis

摘要

The maintenance of multiple ornaments by animals can be explained when those multiple ornaments are sexually selected. However, there have been only a few studies of sexual selection on multiple ornaments. We investigated sexual selection on two ornaments, plumage coloration and white spots in the tail, in a population of Barn Swallows Hirundo rustica gutturalis in Japan. There was sexual dimorphism in throat coloration and in the size of the white spots in the tail. Males with a less saturated (colourful) throat and larger white spots in the tail bred earlier than others, indicating a mating advantage for these males. These trends are what would be expected if these ornaments were indeed sexually selected.