Female Whitebrowed Sparrowweavers Plocepasser mahali trapped on the nest while incubating showed advanced active moult of wing and tail feathers, indicating a complete overlap of moulting and breeding schedules. Additional moult data indicated an unusually protracted primary moult of 183 days. It is suggested that the low daily metabolic demands of a slow moult enable it to be compatible with breeding activities, which may be of advantage to some species living in semi-arid environments.