Numbers, distribution and habitat choice of Whimbrels Numenius phaeopus on spring migration in the Ems-Dollard region, northwest Germany

Whimbrels Numenius phaeopus regularly stopover in the marshes of the Ems-Dollard region in northwest Germany on their way from Africa to the northern breeding areas during spring migration. During the spring (1 March–25 May) of 2012–2019, we counted Whimbrels throughout the lowlands of the River Ems and Dollard Bay. Peak migration was typically at the beginning of May and our maximum weekly counts of individuals ranged between 480–1,366 individuals across years. We identified 14 roost sites in the area that were consistently used throughout the study. Flock size varied between 1–268 individuals. Whimbrels were recorded foraging mainly on intensively farmed grassland in the river lowlands, but also on peaty soil and salt marshes. The feeding areas were around sea level. Only the moraine areas (‘geest’) were not used by Whimbrels. However, the night roosts were situated in shallow water bodies, including tidal mudflats, shallow gravel pits, restored boggy waters and fields in which sludge dredged from the river is spread (‘sludge fields’).