Plumage dimorphism and moult patterns of weaverbirds - a review

The colourful plumages of weaverbirds (family Ploceidae, with 118 species recognised) provide a well-known and in part iconic showcase of sexual selection, with widespread sexual dimorphism (93 species) as well as seasonal dimorphism (62 species). The tremendous diversity in both the type and degree of plumage dimorphism is poorly known, which calls for a better and extended understanding of the highly variable moult patterns in this group. Here, we lay a foundation for this by reviewing and discussing what is known of the timings and patterns of moult in the Ploceidae. The extent of post-juvenile moult is poorly known in weavers: it is known to be complete in 10 species, partial in two species, and either complete or partial in six species. However, it is likely that there is more variation than previously thought. Weavers typically have a complete moult after breeding, and before breeding a partial prenuptial moult, restoring the male (and, in some species, female) breeding plumage; this usually involves only body feathering, one exception being the Seychelles Fody Foudia sechellarum, which has a complete prenuptial moult. We compiled primary moult data based on the proportion of feather mass grown, for 11 weaver species, three of which are newly reported on. Timing of primary moult is discussed in relation to sex, location and annual timing. The duration of primary moult varies widely between and within species, from 46 days (1.5 months) in a widowbird to 215 days (7 months) in an arid species. Weavers in arid regions have longer moult durations than weavers in other regions. Examples of the overlap of primary moult and breeding are presented.