The interplay between moult of flight feathers and fuelling conducted on the breeding grounds of the Great Snipe Gallinago media from the eastern European, lowland population

The Great Snipe as a long-distant migrant wintering in Africa, faces the challenge of accumulating sufficient energy reserves before the departure from European breeding grounds. Despite possible trade-offs in resource allocation, this species additionally initiates moult of flight feathers before southward migration. Here we discuss the strategy of flight feather moult and fuelling, exploring their scheduling, constrained by the timing of breeding and departure for female and male Great Snipes from the European lowland population. We found significant intrasexual differences in both moult initiation date and moult duration. Males start flight feather replacement more than two weeks earlier and moult faster compared to females. However, neither sex completed this process on breeding grounds before the migration, as late in the season all males and half of the females had suspended their primary moult, with the remaining females not moulting at all. Moult of secondaries occurred exceptionally in the studied population. We observed a non-linear energetic stores gain in the studied period, where both sexes maintained a stable and low body condition until the end of July, coinciding with the primary moulting period. Subsequently, there was an increase in body condition, of approximately 1% of the lean body mass per day, indicating a shift towards fuelling for migratory flight. The overlap between stages of maintaining a stable and low body condition and moulting suggests a resource allocation towards feather growth before initiating fuelling. Our study describes moult strategy in Great Snipe conducted on their breeding grounds, highlighting the intrasexual differences, likely resulting from different parental duties of males and females of this lekking species.