LC
Ross's Gull Rhodostethia rosea



Justification

Justification of Red List Category
This species has a very large range, and hence does not approach the thresholds for Vulnerable under the range size criterion (Extent of Occurrence <20,000 km2 combined with a declining or fluctuating range size, habitat extent/quality, or population size and a small number of locations or severe fragmentation). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds under the population trend criterion (>30% decline over ten years or three generations). The population size may be moderately small to large, but it is not believed to approach the thresholds for Vulnerable under the population size criterion (<10,000 mature individuals with a continuing decline estimated to be >10% in ten years or three generations, or with a specified population structure). For these reasons the species is evaluated as Least Concern.

Population justification
The global population is estimated to number c.25,000-100,000 individuals (Wetlands International 2016). At least 20,000 (up to 38,000) individuals move past Point Barrow, Alaska, in autumn (Maftei et al. 2014). The population in Russia has been estimated at c.100-10,000 breeding pairs and c.50-1,000 individuals on migration (Brazil 2009). The population in Greenland is estimated at 0-5 pairs (BirdLife International 2015).

Trend justification
The population trend is difficult to determine because of uncertainty over the extent of threats to the species (del Hoyo et al. 1996).

Distribution and population

This species breeds in the high Arctic of North America and Siberia. It is found in north-east Siberia, Russia, from the Taymyr Peninsula to the Kolyma River, locally in Greenland (to Denmark) and irregularly in Canada. Its wintering range in Siberia expands further west and east down to the tip of the Kamchatkan Peninsula, with other wintering sites including the north coast of Alaska (U.S.A.) and the south-eastern coast of Greenland (del Hoyo et al. 1996).

Ecology

Behaviour This species is migratory and travels north after breeding to overwinter in the Arctic Ocean (del Hoyo et al. 1996, Snow and Perrins 1998). It arrives on its breeding grounds in late-May, where it breeds from early-June in loose colonies of 2-10 pairs (rarely up to 18 pairs) often with other species (e.g. Arctic Tern Sterna paradisaea) (del Hoyo et al. 1996, Snow and Perrins 1998). The departure from the breeding grounds occurs from late-July onwards, with the species migrating in small flocks of 2-16 individuals (del Hoyo et al. 1996). It forages solitarily or in small loose flocks (del Hoyo et al. 1996).
Habitat Breeding The species breeds in the upper boreal forest (taiga) and tundra zones of the high Arctic, showing a preference for nesting on small, low islets in shallow pools (created by snow-melt on tundra underlain with permafrost) surrounded by stands of stunted alder Alnus spp. and willow Salix spp. and by muddy, boggy or marshy ground with sedges and moss (Richards 1990, del Hoyo et al. 1996, Snow and Perrins 1998, Olsen and Larsson 2003). The species also breeds on marshy tundra in high Arctic river deltas and on marshy ground in well-wooded river valleys (Richards 1990, del Hoyo et al. 1996). Non-breeding Outside of the breeding season, the species forages pelagically on the open sea or along the edges of pack-ice (del Hoyo et al. 1996).
Diet Breeding On its breeding grounds, the species is chiefly insectivorous, its diet including Coleoptera and dipteran flies (Richards 1990, del Hoyo et al. 1996). Non-breeding On migration and in the winter, its diet consists of small fish and surface-dwelling marine invertebrates (including plankton, crustaceans, molluscs and priapulid marine worms) (del Hoyo et al. 1996, Snow and Perrins 1998).
Breeding site The nest is constructed of dry grass, sedge and moss, usually on a tussock on an island in a pool in tundra or forest (del Hoyo et al. 1996). The species nests in near invisible colonies, often with other species, with an average distance between neighbouring nests of 43 m (del Hoyo et al. 1996).

Threats

The species is strongly associated with areas of sea ice, especially in the post-breeding period (Gilg et al. 2016), and the alteration in ice distribution and indeed ongoing loss of ice may have already caused a shift in a least a portion of the species's annual movements (Joiris 2017). More research is urgently required, particularly as breeding success appears to be very low (typically less than 33%) (Burger et al. 2018). The species also faces a number of more direct human threats, such as nest failures as a result of human disturbance in Canada (Burger et al. 2018) and being shot by native Alaskan peoples for food (Burger et al. 2018). These, however, do not seem to be causing a significant decline.

Conservation actions

Conservation Actions Underway
Listed under the African Eurasian Waterbird Agreement.

Conservation Actions Proposed
Identification of Important Bird Areas in Arctic, including for sites at sea, and subsequent designation as marine protected areas. Carry out surveys to determine robust estimate of global population.

Acknowledgements

Text account compilers
Calvert, R., Butchart, S., Ekstrom, J., Malpas, L., Ashpole, J, Martin, R., Stuart, A.


Recommended citation
BirdLife International (2020) Species factsheet: Rhodostethia rosea. Downloaded from http://www.birdlife.org on 30/09/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 30/09/2020.