Factors influencing the evolution of moult in the non-breeding season: insights from the family Motacillidae

Abstract

The number of moults per annual cycle and their final spatial pattern (i.e. topography) show high interspecific variation in the order Passeriformes. Factors behind this variability remain obscure, especially for variability in spatial pattern among species. Here, we explored the relative influence of ten ecological, ontogenetic, social and sexual factors on the evolution of autumn moult (feather replacement largely undertaken by migratory species, which is not necessarily an independent episode within their moult cycle) and prealternate moult among Northern Hemisphere species of the family Motacillidae using phylogenetically controlled analyses, ancestral state reconstruction and analyses of correlated evolution. The results strongly support the presence of prealternate moult and absence of autumn moult as ancestral states in this family. A high rate of change between related species indicates phylogenetic independence among prealternate moult patterns and examined factors. Migration distance and gregariousness are the most important factors influencing prealternate moult evolution, and point toward natural selection and sociality as the most important evolutionary drivers of prealternate moult in Motacillidae. Breeding latitude, seasonal plumage change, winter plumage conspicuousness, sexual dichromatism, plumage maturation and extent of preformative moult show a minor influence, and suggest that ontogeny and sexual selection may have played a limited role in shaping prealternate moult in Motacillidae.

Convergence of biannual moulting strategies across birds and mammals

“…In endotherms that inhabit higher latitudes, plumages and pelages play distinct seasonal roles [10] in camouflage ( pelage colour polyphenism [129]), insulation and mate attraction. In birds, the biannual moult evolved from the ancestral state of a single summer moult [11,132,133] as a response to energetic and environmental selection factors. We suggest that the same could be true in mammals, giving the moult similar adaptive functions across avian and mammalian taxa.…”

Evolutionary drivers of seasonal plumage colours: colour change by moult correlates with sexual selection, predation risk and seasonality across passerines

“…Crypsis to predators may also be especially favoured in winter or during the non-breeding season, when resources are scarce and an increased risk of starvation lowers the capacity of birds to maintain high levels of antipredator behaviour (Macleod et al 2005;Cox et al 2011). In addition, migrants and species adapted to strong temperature seasonality often moult twice to replace worn feathers or increase plumage insulation during winter (Guallar & Figuerola 2016;Beltran et al 2018). This adaptation may facilitate the secondary evolution of seasonal plumage colours (Howell 2010;Guallar & Figuerola 2016;Beltran et al 2018).…”

“…In addition, migrants and species adapted to strong temperature seasonality often moult twice to replace worn feathers or increase plumage insulation during winter (Guallar & Figuerola 2016;Beltran et al 2018). This adaptation may facilitate the secondary evolution of seasonal plumage colours (Howell 2010;Guallar & Figuerola 2016;Beltran et al 2018).…”

Adaptive plumage wear for increased crypsis in the plumage of Palearctic larks (Alaudidae)

“…Nonetheless, a majority of Palearctic larks (and perhaps African ones too, although precise data are lacking) initiate their aerial courtships in spring with a highly worn plumage, and they actually breed and raise their young in the most worn state of the plumage before the next molt. Most songbirds follow a different strategy from the larks and start breeding in rather prime plumage condition, many of them having previously undergone the prealternate molt, involved in the formation of a fresh, attractive plumage thought to be sexually selected for mate acquisition (Guallar and Figuerola 2016). Only 10 other species of different families are shown in fresh and worn plumages out of about 700 species covered in the guide.…”

“…Only 10 other species of different families are shown in fresh and worn plumages out of about 700 species covered in the guide. Most songbirds follow a different strategy from the larks and start breeding in rather prime plumage condition, many of them having previously undergone the prealternate molt, involved in the formation of a fresh, attractive plumage thought to be sexually selected for mate acquisition (Guallar and Figuerola 2016).…”