Annual movements of a migratory seabird—the NW European red-throated diver (Gavia stellata)—reveals high individual repeatability but low migratory connectivity

Abstract

In this study, the annual movements of a seabird species, the red-throated diver (Gavia stellata), were investigated in space and time. Between 2015 and 2017, 33 individuals were fitted with satellite transmitters at the German Bight (eastern North Sea). In addition, stable isotope analyses of feathers (δ13C) were used to identify staging areas during the previous moult. The German Bight is an important area for this species, but is also strongly affected by anthropogenic impacts. To understand how this might affect populations, we aimed to determine the degree of connectivity and site fidelity, and the extent to which seasonal migrations vary among different breeding locations in the high Arctic. Tagged individuals migrated to Greenland (n = 2), Svalbard (n = 2), Norway (n = 4) and northern Russia (n = 25). Although individuals from a shared breeding region (northern Russia) largely moved along the same route, individuals dispersed to different, separate areas during the non-breeding phase. Kernel density estimates also overlapped only partially, indicating low connectivity. The timing of breeding was correlated with the breeding longitude, with 40 days later arrival at the easternmost than westernmost breeding sites. Repeatability analyses between years revealed a generally high individual site fidelity with respect to spring staging, breeding and moulting sites. In summary, low connectivity and the distribution to different sites suggests some resilience to population decline among subpopulations. However, it should be noted that the majority of individuals breeding in northern Russia migrated along a similar route and that disturbance in areas visited along this route could have a greater impact on this population. In turn, individual site fidelity could indicate low adaptability to environmental changes and could lead to potential carry-over effects. Annual migration data indicate that conservation planning must consider all sites used by such mobile species.

Large-scale effects of offshore wind farms on seabirds of high conservation concern

“…All data for up to 35 km from any wind farm were used. Larger distances were not expected to disturb the birds though the home range sizes of satellite-tracked birds 62 suggest that they would be able to commute over such distances.…”

Prevalence of Haemosporidian Parasites in an Arctic Breeding Seabird Species—The Red-Throated Diver (Gavia stellata)

“…Bird capture and sampling were carried out in accordance with the local legislation. Sampling was conducted in the eastern German Bight (North Sea Germany) about 20 to 30 km west of the island of Amrum in three consecutive years: March to April 2015, February to March 2016 and March 2017 [31,[38][39][40][41][42]. A total of 45 red throated divers were captured to be tagged with satellite transmitters within the study area.…”

“…The breeding regions of red-throated divers in this data set were identified by additional analysis of tracking data and were located in Greenland, Svalbard, Norway and northern Russia, see Kleinschmidt et al [40], (Figure 2). The breeding regions of two individuals, one (ID 146445) infected with Leucocytozoon and one (ID 146441) that showed a heterogenic infection with Leucocytozoon and Plasmodium, could not be assigned due to the early mortality of these individuals.…”

“…We took blood samples from 45 red-throated divers captured between 54 • N 7 • E and 55 • N 8 • E in an internationally important non-breeding habitat, the eastern German Bight (North Sea) in winter and spring within the framework of the DIVER project [31,[38][39][40][41][42]. The DIVER project is a tracking study, and therefore information on the breeding areas in Greenland (−20 N) of single individuals was available to be linked with haemosporidian parasite infection.…”