Population status and trend of the threatened ivory gull Pagophila eburnea in Svalbard

The ivory gull Pagophila eburnea is a high-Arctic seabird associated with sea ice throughout the year. It breeds at high latitudes, mostly in the Atlantic sector of the Arctic. It is rare (<11500 breeding pairs globally) and remains one of the most poorly known seabirds in the world. Although Svalbard (Norway) supports breeding populations of international significance, the population trend in the region was unknown prior to this study. We conducted annual surveys of known breeding sites from 2006 to 2019 to estimate the size of the ivory gull population in Svalbard and to assess the population trend. We visited 117 colonies, 60 of which were new discoveries during this study. All breeding sites were situated in cliffs, and no ground-breeding ivory gulls were found. Based on the most complete survey in 2019, we estimated the Svalbard breeding population to be between 1500 and 2000 breeding pairs. We recorded an overall 40% decline in the number of breeding ivory gulls, but the trends varied significantly among colonies. The inter-annual fluctuations in the number of breeding pairs were not synchronous among colonies, which can be explained by the movements of adult breeding birds between colonies. The current decline in the Svalbard ivory gull population could be related to the ongoing decline in sea ice extent and quality in the Barents Sea. It may also be driven by ecological changes along the migration routes or at the wintering grounds, as hypothesized for the Canadian breeding population.

Seabird and Marine Mammal at-sea Distribution in the Norwegian, Greenland and Wandel Seas, 2018

Quantitative seabird and marine mammal at-sea distribution was determined in the Norwegian, Greenland and Wandel seas in August 2018 on board the icebreaking RV Polarstern. A total of 7,380 seabirds belonging to 25 species were tallied during 380 transect counts lasting 30 minute each, i.e. a mean value of 19 per count. Cetaceans were represented by seven species (mean of 0.1 per count) and pinnipeds by four species (0.1 per count). Numbers of seabird species and of individuals were low in the Norwegian Sea and the Greenland Sea (12 and 14 species, 4 and 8 individuals per count). They were especially low in the Wandel Sea off North Greenland: seven seabird species (2 individuals per count), mainly ivory gull Pagophila eburnea and fulmar Fulmarus glacialis. Cetaceans were absent and pinnipeds represented by three species only (0.3 per count). These concentrations are extremely low even when compared to other areas of the high Arctic Ocean.

Living on the edge of a shrinking habitat: the ivory gull, Pagophila eburnea , an endangered sea-ice specialist

The ongoing decline of sea ice threatens many Arctic taxa, including the ivory gull. Understanding how ice-edges and ice concentrations influence the distribution of the endangered ivory gulls is a prerequisite to the implementation of adequate conservation strategies. From 2007 to 2013, we used satellite transmitters to monitor the movements of 104 ivory gulls originating from Canada, Greenland, Svalbard-Norway and Russia. Although half of the positions were within 41 km of the ice-edge (75% within 100 km), approximately 80% were on relatively highly concentrated sea ice. Ivory gulls used more concentrated sea ice in summer, when close to their high-Arctic breeding ground, than in winter. The best model to explain the distance of the birds from the ice-edge included the ice concentration within approximately 10 km, the month and the distance to the colony. Given the strong links between ivory gull, ice-edge and ice concentration, its conservation status is unlikely to improve in the current context of sea-ice decline which, in turn, will allow anthropogenic activities to develop in regions that are particularly important for the species.

Rapidly increasing methyl mercury in endangered ivory gull ( Pagophila eburnea ) feathers over a 130 year record

Mercury (Hg) is increasing in marine food webs, especially at high latitudes. The bioaccumulation and biomagnification of methyl mercury (MeHg) has serious effects on wildlife, and is most evident in apex predators. The MeHg body burden in birds is the balance of ingestion and excretion, and MeHg in feathers is an effective indicator of overall MeHg burden. Ivory gulls ( Pagophila eburnea ), which consume ice-associated prey and scavenge marine mammal carcasses, have the highest egg Hg concentrations of any Arctic bird, and the species has declined by more than 80% since the 1980s in Canada. We used feathers from museum specimens from the Canadian Arctic and western Greenland to assess whether exposure to MeHg by ivory gulls increased from 1877 to 2007. Based on constant feather stable-isotope ( δ 13 C, δ 15 N) values, there was no significant change in ivory gulls' diet over this period, but feather MeHg concentrations increased 45× (from 0.09 to 4.11 µg g −1 in adults). This dramatic change in the absence of a dietary shift is clear evidence of the impact of anthropogenic Hg on this high-latitude threatened species. Bioavailable Hg is expected to increase in the Arctic, raising concern for continued population declines in high-latitude species that are far from sources of environmental contaminants.