Primary wing-moult in relation to body-mass, wing-length and latitude in four insectivorous passerines from southern Africa

Abstract

In southern African passerine birds, the timing of moult often varies regionally in relation to breeding season and patterns of rainfall, and may also differ between sexes in sexually dimorphic species. However, the relationship between feeding ecology andmoult has not been studied in this region. We investigated primary-moult, body-mass and wing-length in four southern African passerines belonging to a feeding guild of hawking (sallying) insectivores, using bird-banding (ringing) data. The timing of wing-moult, from December to April throughout the region, was very similar in all four species, in contrast to other sympatric species, which moult at different times in summer-and winter-rainfall regions. For each species the duration of moult decreased southwards, as did wing-length corrected for body-mass. There was no difference between the sexes in the timing or duration of wing-moult, even in sexually dimorphic species, but juveniles generally started moult later than adults and completed their moult more rapidly. Our results suggest that foraging ecology and life-history traits of insectivorous hawkers may constrain the timing of moult.