Justification of Red List Category
This species has an extremely 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 appears to be stable, and hence the species does not approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is very large, and hence does not 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.
The global population is estimated at 190,000-400,000 individuals by Wetlands International (2015). The European population is estimated at 50,000-100,000 pairs, which equates to 100,000-200,000 mature individuals or 150,000-300,000 individuals (BirdLife International 2015). Combining the recently published population estimate for the European population with the Wetlands International (2015) estimate provides a new global population estimate of 250,000-400,000 individuals, here placed in the band 100,000-499,999 individuals.
The overall population trend is stable (Wetlands International 2015). This species has undergone a large and statistically significant increase over the last 40 years in North America (2,200% increase over 40 years, equating to a 117% increase per decade; data for Larus glaucoides and L. thayeri combined, from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007). The European population trend estimate is stable (BirdLife International 2015).
This species breeds in the Arctic regions of Canada and Greenland (to Denmark), and outside the breeding season can be found wintering in the northernmost states of the eastern U.S.A. as far inland as the great lakes, on Iceland, Ireland, the United Kingdom, the north coast of Norway, the southern tip of Scandinavia and the northern tip of Germany (del Hoyo et al. 1996).
Behaviour Northernmost populations of this species are strongly migratory whereas others (e.g. in Greenland) only disperse locally along the coast after breeding (del Hoyo et al. 1996). The species breeds from mid-May to July (Richards 1990) in solitary pairs or in small single- or mixed-species colonies (del Hoyo et al. 1996) of up to several hundred pairs (Snow and Perrins 1998). In late-July after breeding the species may move to coastal feeding areas, the departure from the breeding grounds occurring in August or September (del Hoyo et al. 1996). Habitat The species inhabits rocky coasts and fjords with steep cliffs (Richards 1990), offshore stacks and undisturbed low islands for nesting on, also foraging in the intertidal zone (del Hoyo et al. 1996). After breeding the species remains in similar habitats (Snow and Perrins 1998) but often disperses to harbours, refuse tips, sewage outfalls and inland reservoirs, although it generally avoids freshwater habitats (del Hoyo et al. 1996). Diet Its diet consists predominantly of small fish (e.g. salmon Salmo spp., sprat Sprattus spp. and herring Clupea spp.) and marine invertebrates as well as bird eggs and chicks (del Hoyo et al. 1996) (especially of Black-legged Kittiwake Rissa tridactyla) (Snow and Perrins 1998), seeds and fruits (del Hoyo et al. 1996). Breeding site The nest is constructed of dry grass, seaweed and moss on large, flat ledges of steep coastal cliffs greater than 100-200 m in height (Richards 1990, del Hoyo et al. 1996), or on offshore stacks or on the ground on undisturbed low coastal islands (del Hoyo et al. 1996).
Utilisation The species is extensively hunted by local people in Greenland, and increased non-native predators could also pose a hazard during the breeding season (Burger and Gochfeld 1996).
Conservation Actions Underway
The following information refers to the species's European range only: The species is covered under the African Eurasian Waterbird Agreement. In Europe there are two marine Important Bird Areas identified for this species (Greenland). Within the EU, there are two Special Protection Areas (Spain and Portugal).
Conservation Actions Proposed
The following information refers to the species's European range only: Identification of important sites for this species and subsequent designation as protected areas. Eradication of invasive predators from breeding sites. Continued monitoring of numbers caught for consumption.
Text account compilers
Ashpole, J, Butchart, S., Calvert, R., Ekstrom, J., Malpas, L.
BirdLife International (2018) Species factsheet: Larus glaucoides. Downloaded from http://www.birdlife.org on 14/11/2018. Recommended citation for factsheets for more than one species: BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 14/11/2018.