Evolution of winter moulting strategies in European and North American migratory passerines

Moult is critical for birds as it replaces damaged feathers and worn plumage, enhancing flight performance, thermoregulation, and communication. In passerines, moult generally occurs on the breeding grounds during the post-breeding period once a year. However, some species of migrant passerines that breed in the Nearctic and western Palearctic regions have evolved different moulting strategies that involve moulting on the overwintering grounds. Some species forego moult on the breeding grounds and instead complete their prebasic moult on the overwintering grounds. Other species moult some or all feathers a second time (prealternate moult) during the overwintering period. Using phylogenetic analyses, we explored the potential drivers of the evolution of winter moults in Nearctic and western Palearctic breeding passerines. Our results indicate an association between longer photoperiods and the presence of prebasic and prealternate moults on the overwintering grounds for both Nearctic and ...