The flexibility of primary moult in relation to migration in Palaearctic waders – an overview

This paper presents an overview of patterns in the primary moult of waders using the Eurasian–African migration system and updates earlier summaries with results obtained from the Underhill–Zucchini moult models (1988, 1990). Recent applications of these models allow researchers to examine moult timing down to the progress of an individual feather in a tract and to determine the effects of environmental factors on moult. Waders present a wide variety of inter- and intra-specific strategies for their primary moult, an energy-costly activityrthey must fit in with breeding and migration, the other main energy-demanding events in their life cycle. Here I present the moult strategies of waders in the context of their age, size, sex and annual variation in breeding success, seasonal food abundance, the latitude where they moult, the distance they migrate, the habitats they use, and the rainfall patterns and temperatures at their moulting grounds. I also discuss how moult is adjusted to these factors. This overview emphasises the flexibility of many waders’ moult strategies as an adaptation to the unpredictable food supply provided by ephemeral inland wetlands and compares these strategies with those of populations that use predictable coastal habitats. Discovering the mechanisms that allow waders to adjust their genetically controlled and hormonally regulated moult to proximate factors is suggested as one of the challenges in further studies of moult.