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- Data packageData from: Underestimated scale of songbird offshore migration across the south-eastern North Sea during autumn(2021-11-04) Brust, Vera; Hüppop, OmmoFlights over open water can be challenging for migrating songbirds. Despite numerous observations of songbirds migrating over remote islands, virtually nothing is known about the proportion of songbirds risking to fly offshore rather than to follow the coastline. By means of large-scale automated radio-telemetry, we individually tracked songbirds during their autumn migration through the German Bight area in the south-eastern North Sea. Our tracking network facilitated the recording of movement patterns over the bay and, for the first time, the estimation of the proportions of individuals embarking on offshore flights from their coastal stopover sites. Our data are consistent with previous observations of decreasing migration densities from nearshore to offshore, i.e. from east to west in autumn. Still, we revealed a considerable proportion of 25% of birds flying offshore. The tendency to fly offshore decreased from west to south migrants, which is in line with optimal bird migration theory. Among south-west migrating species, which also comprise the vast majority of songbird species migrating through the German Bight area, thrushes showed the highest proportions of offshore flights. Considering the recent and ongoing increase of artificial offshore structures, our results suggest that some species or species groups might especially face an increased risk of being negatively affected.
- Data packageData from: Are movements of day- and night-time passerine migrants as different as day and night?(2020-09-08) Michalik, Bianca; Brust, Vera; Hueppop, OmmoEven after decades of research, the migration of songbirds still holds numerous secrets. Distinct stopover and routing behavior of diurnally and nocturnally migrating songbirds has been stated in the 1960s, but empirical confirmation is yet lacking widely. We studied the behavior of individual diurnally migrating dunnocks and nocturnally migrating blackcaps by means of large‐scale automated radio‐telemetry. Birds were radio‐tagged during their stopover at the German North Sea coast. Our data indicate longer initial stopover duration in the diurnally migrating dunnocks, opposing the hypothesis of nocturnal migrants needing more time to recover due to their longer migratory flights. Nonetheless, dunnocks stopped over more often along their tracks as when compared to the nocturnally migrating blackcaps. Behavior en route did not differ as clearly between species challenging the general view of contrasting routings of diurnal and nocturnal migrants with regard to landscape and open water. Our results imply additional factors of relevance other than differences in species or daily migration timing per se. We discuss and highlight the need of detailed and individual based data to better understand stopover and routing behavior of songbirds in the environmental context.