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 global population trend is stable (Wetlands International 2015). In North America, the species has undergone a large and statistically significant increase over the last 40 years (2,200% increase over 40 years, equating to a 117% increase per decade; data 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). Outside the breeding season, it can be found wintering on the Pacific coast from south-east Alaska (U.S.A.) to north Baja California (Mexico), as well as 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 long-distant migrants moving south in the non-breeding season (del Hoyo et al. 1996, Olsen and Larsson 2003). Other populations, e.g. from Greenland, only disperse locally along the coast after breeding (del Hoyo et al. 1996). The species breeds from mid May to July in solitary pairs or in small single- or mixed-species colonies of up to several hundred pairs (Richards 1990, Gaston 1991, del Hoyo et al. 1996, Snow and Perrins 1998), often near nesting Larus hyperboreus (del Hoyo et al. 1996). In late July, the species may move to coastal feeding areas. It departs from the breeding grounds in August or September (del Hoyo et al. 1996) and arrives on its wintering grounds between late October and December, where it remains until April (Alderfer 2006). It is gregarious throughout the year (del Hoyo et al. 1996, Olsen and Larsson 2003) and may occur in large flocks at favoured sites during the winter (Olsen and Larsson 2003, Sibley 2003), although it usually occurs in small numbers amongst larger flocks of other gull species (Sibley 2003). It forages in the intertidal zone, but may also follow fishing boats with other species of gull (del Hoyo et al. 1996). Habitat Breeding For breeding the species requires rocky coasts and fjords with steep cliffs (Richards 1990, Gaston 1991, del Hoyo et al. 1996, Olsen and Larsson 2003). It occurs up to 3 km inland along Arctic shores, offshore stacks and undisturbed low, rocky islands (Godfrey 1979, Gaston 1991, del Hoyo et al. 1996). Non-breeding During the winter, the species frequents a variety of habitats surrounding coastal shores and estuaries, often foraging around fishing harbours, inland reservoirs, refuse dumps and settlements (del Hoyo et al. 1996, Olsen and Larsson 2003, Alderfer 2006). It may also occur on inland freshwater lakes, rivers, flooded land and occasionally agricultural fields especially when on migration (Godfrey 1979, Olsen and Larsson 2003), 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 (especially of Black-legged Kittiwake Rissa tridactyla), seeds and fruits (del Hoyo et al. 1996, Snow and Perrins 1998).
Breeding site The nest is constructed of dry grass, seaweed and moss. It is placed on large, flat ledges of steep coastal cliffs greater than 100-200 m in height, on offshore stacks, surrounding a near-coastal freshwater sites or on the ground on undisturbed low coastal islands (Godfrey 1979, Richards 1990, del Hoyo et al. 1996, Olsen and Larsson 2003).
The species is extensively hunted by local people in Greenland, and non-native predators could also pose a hazard during the breeding season (Burger and Gochfeld 1996). However, this is not thought to pose a significant threat to the species.
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
Ekstrom, J., Ashpole, J, Butchart, S., Hermes, C., Malpas, L., Calvert, R.
BirdLife International (2019) Species factsheet: Larus glaucoides. Downloaded from http://www.birdlife.org on 22/03/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 22/03/2019.