Preening, plumage reflectance and female choice in budgerigars

Plumage ornaments are important signals in sexual selection context. Plumage maintenance is therefore important not only for insulation and flight but also for ornament efficacy. However, the effect of plumage maintenance on ornament characteristics and female choice has never been investigated experimentally. In this study we focused on the influence of preening on plumage reflectance and, indirectly, on female preference in the budgerigar Melopsittacus undulatus. We measured the effect of preening on the reflectance of previously soiled plumage. Our results suggest that soiling affects plumage reflectance in budgerigars that are prevented from preening and that this effect is particularly pronounced in the UV range. In contrast, individuals that were allowed to preen restored their plumage reflectance spectrum to presoiling levels. In a two-choice test, females presented with clean (preened) and soiled (unpreened) males, spent more time near the clean male. These results suggest that female budgerigars are able to discriminate between preened and unpreened males. Further investigations, conducted under various soiling conditions, are necessary to confirm the effect of soiling on plumage reflectance spectrum and to investigate which cues are used by females to discriminate between preened and unpreened males. Such research could reveal whether UV feather ornaments, mediated by preening, are special signals conveying information about a bird's current condition.