Behaviors of Grey Seals (Halichoerus Grypus) Addressed Towards Human Swimmers During Experimental Open Water Encounters Off Heligoland (German Bight, North Sea)

Risks arising for humans during swim encounters with seals are poorly understood. This study was initiated to examine behaviors of unhabituated grey seals addressed towards humans during experimental, noncommercial seal-swim activities off Heligoland. In total, 26 in-water encounters were conducted. Behavioral classes and the number of seals simultaneously approaching swimmers were time sampled. A set of risky and nonrisky interactive behaviors was continuously sampled. Seals spent approximately the same amount of time interacting with swimmers (53%) as they did ignoring them (47%). Seals displayed higher rates of nonrisky behaviors than risky ones, but risky behaviors occurred during 73% of all seal-swims. Seals remained ≤20 m near swimmers for 51% and ≤1 m for 13% of the time. A mean number of 0.65 and 0.18 seals approached swimmers per minute within a range of ≤20 m and ≤1 m, respectively. Behavioral classes, interactive behaviors, and the number of seals approaching ≤20 m did not vary significantly throughout seal-swims but the number of seals approaching ≤1 m moderately decreased. Due to high rates of risky behaviors, it is recommended to promote public awareness on site and to regulate seal-swims before commercial operations emerge.

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Underestimated scale of songbird offshore migration across the south-eastern North Sea during autumn

Journal of Ornithology ◽

10.1007/s10336-021-01934-5 ◽

2021 ◽

Author(s):

Vera Brust ◽

Ommo Hüppop

Keyword(s):

North Sea ◽

German Bight ◽

Large Scale ◽

Radio Telemetry ◽

Open Water ◽

Offshore Structures ◽

Considerable Proportion ◽

The South ◽

South Eastern ◽

Increased Risk

AbstractFlights 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.

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