Sexual ornaments are conspicuous characters used in mate choice and intrasexual competition. Plumage coloration is among the most widely studied sexual ornaments. We focus on two scarcely known topics related to plumage colour. The first topic is the role of feather nanostructural variability in determining the light reflectance attributes of white plumage areas, a widespread but neglected ornament type in birds. Our previous work on collared flycatcher plumage reflectance suggested that the brightness and the UV chroma of white areas change differently and are therefore likely modulated by different background mechanisms. In this project, we examine these mechanisms. Our second topic is the magnitude and importance of rapid plumage reflectance change during the breeding event. This has great evolutionary and practical implications, yet it is essentially unknown. We have previously found that male flycatcher plumage shows variable degrees of UV chroma decline from courtship to nestling rearing, and we detected relationships between plumage reflectance and the reproductive behaviour of the partner. We therefore hypothesize that plumage UV reflectance may be a dynamic trait that conveys actual information on the individual to the partner. We conduct similar studies on plumage traits of other species as well.
The project is supported by the National Research, Development and Innovation Office (NKFIH K124443).