Environmental, genetic and fitness correlates of male seasonal plumage ornaments in a genetically monogamous bird

Elaborate ornamentation is often assumed to improve reproductive success of the bearer, by attracting mates or deterring rivals. In particular, bright plumage in birds may signal the quality of an individual, provided that its production and maintenance are costly. Seasonal plumages, i.e. the alternation of dull non-breeding plumage and colourful breeding plumage, have the potential to do so through multiple components; however, the nature and magnitude of their benefits and costs remain ill-understood, particularly for species that form monogamous, year-round and long-term partnerships. Here I investigate the function of male seasonal plumages in the genetically monogamous purple-crowned fairy-wren, Malurus coronatus.