Seasonal Variation in the Diet of Migratory Shorebirds Wintering in the Bijagós Archipelago, Guinea-Bissau

Abstract

As on intertidal flats across the globe, the migratory shorebirds that spend most of their annual cycle in the Bijagós Archipelago, Guinea-Bissau, feed on macrozoobenthic prey buried in the intertidal soft sediments. Understanding the diet of shorebirds throughout the period of residence in the Bijagós can help to understand the degree of their trophic flexibility. In this study, we first reconstruct the diet of eight migratory shorebirds in the Bijagós, then investigate how their diet changes throughout the three main periods of the non-breeding season (arrival, mid-winter and fuelling periods) and finally explore the intraspecific dietary overlap between the three periods. We found significant changes in the diet of most shorebirds across the three periods, with some smaller species increasing the proportion of polychaetes in their diet in the fuelling period, while larger species increased the proportion of bivalves. The fuelling period showed the lowest overlap values with the other two periods, confirming that during this time most shorebirds considerably changed their diet, which may either reflect changes in prey availability or in prey selection.