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). Despite the fact that the population trend appears to be decreasing, the decline is not believed to be sufficiently rapid to approach the thresholds for Vulnerable under the population trend criterion (>30% decline over ten years or three generations). The population size is extremely 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 to number c. 14,600,000-15,700,000 (Wetlands International 2016). The European population is estimated at 1,730,000-2,200,000 pairs, which equates to 3,460,000-4,410,000 mature individuals (BirdLife International 2015).
The population trend is decreasing in North America (based on BBS/CBC data: Butcher and Niven 2007). In Europe the population size is estimated and projected to decrease by 30-49% over the period from 1983, the start year of the reported trend for Iceland, which accounts for more than 30% of the European population) to 2020 (three generations). , although populations are stable or have unknown trends elsewhere (Wetlands International 2016).
This species nests along coastlines in much of the north Pacific and Atlantic oceans, and also breeds on inlands off the northern coast of Russia and on the northern coast of Norway. It winters at sea, ranging across much of the north Atlantic and Pacific oceans (del Hoyo et al. 1996). Overall population trends are unknown, though failed breeding seasons in 2008 and in some cases significant population declines have been observed in the United Kingdom by the RSPB.
Behaviour This species is migratory and disperses after breeding from coastal areas to the open ocean (del Hoyo et al. 1996). It returns to its breeding grounds from January where it breeds from mid-May to mid-June in huge single- or mixed-species colonies (del Hoyo et al. 1996) that often exceed 100,000 pairs (del Hoyo et al. 1996, Snow and Perrins 1998). Breeding may occur later after periods of cold weather and many individuals do not remain on the breeding grounds during such conditions (del Hoyo et al. 1996). The species begins to disperse from the breeding colonies between July and August, often moulting in large flocks of several thousand individuals on beaches between the breeding grounds and the open sea (Olsen and Larsson 2003). Non-breeders may also remain at sea during the breeding season (Snow and Perrins 1998). Outside of the breeding season the species often occurs singly or in pairs (Snow and Perrins 1998) but may also occur in small flocks or as dispersed aggregations (Flint et al. 1984, Snow and Perrins 1998). Habitat Breeding It nests on high, steep coastal cliffs with narrow ledges in areas with easy access to freshwater (del Hoyo et al. 1996). Non-breeding The species moults on sandy beaches (Olsen and Larsson 2003) and on passage it may concentrate at sea on continental shelves, areas of upwelling (del Hoyo et al. 1996) and at rich fish banks (Olsen and Larsson 2003). During the winter the species is highly pelagic, usually remaining on the wing out of sight of land (del Hoyo et al. 1996). Diet Its diet consists predominantly of marine invertebrates (e.g. squid and shrimps) and fish, although during the breeding season it may also take intertidal molluscs, crustaceans (del Hoyo et al. 1996) (e.g. crayfish) (Flint et al. 1984), earthworms, small mammals and plant matter (e.g. aquatic plants, potato tubers and grain) (del Hoyo et al. 1996). At sea during the winter it will also take planktonic invertebrates and often exploits sewage outfalls and fishing vessels (del Hoyo et al. 1996). Breeding site The nest is a compacted mass of mud (Snow and Perrins 1998), grass and feathers (Flint et al. 1984) usually built on a narrow ledge on high, steep coastal cliffs (del Hoyo et al. 1996). Occasionally the species may also nest on glaciers or snow banks (where these have covered traditional cliff nesting sites), on buildings and piers, or on flat, rocky or sandy sites up to 20 km inland (del Hoyo et al. 1996). It breeds in very large colonies with neighbouring nests spaced evenly 30-60 cm apart (where site availability allows) (Snow and Perrins 1998), and generally feeds within 50 km of the breeding colony (del Hoyo et al. 1996).
The species is threatened by the depletion of food resources (e.g. through over-fishing) (Frederiksen et al. 2004, Nikolaeva et al. 2006), marine oil spills (del Hoyo et al. 1996, Nikolaeva et al. 2006) and chronic oil pollution (Nikolaeva et al. 2006). It is also susceptible to avian influenza so may be threatened by future outbreaks of the virus (Melville and Shortridge 2006). The species is potentially threatened by climate change because it has a geographically bounded distribution: its global distribution is restricted to within c.10o latitude from the polar edge of continent and within which 20-50% of current vegetation type is projected to disappear under doubling of CO2 levels (BirdLife International, unpublished data). It is caught as bycatch in longline fisheries, with significant numbers estimated to be caught off the western coast of Ireland and the U.K.. The species is considered a high risk for collision with offshore wind farms (Bradbury et al. 2014). The species is hunted in the Faroe Islands and in Greenland (Labansen et al. 2010, Thorup et al. 2014, Burger et al. 2016).
Conservation Actions Underway
The species is listed under the African-Eurasian Waterbird Agreement, but is not listed on the Bern Convention, the Convention of Migratory Species or on the EU Birds Directive Annexes. It is protected in some European countries by national legislation, including: France (‘Liste des espèces d’oiseaux protégées en France en application de l’article L. 411-1 du code de l’environnement et de la directive 79/409 du 2 avril 1979 concernant la conservation des oiseaux sauvages’); Portugal (D.L. 140/99 de 24 de Abril rectificado pelo D.L. 49/2005 de 24 de Fevereiro; Spain (species listed on the State Catalogue of Threatened Species as a species of “Special Interest” – Royal Decree 439/1990 & under regional legislation and included on the Galician Catalogue of Threatened Species: “Vulnerable” Decree 82/2007 of 19th of April). The species is categorised as Vulnerable in the Norwegian Red List and the All-Ireland Vertebrate Red Data Book (OSPAR 2010). Population monitoring occurs across much of its breeding range, including Greenland, Norway (Anker-Nilssen et al. 2007), Iceland (Garðarsson 2006) France and the U.K.. The species is considered within the Nordic Action Plan for Seabirds.
Conservation Actions Proposed
The species could benefit from regional level, international Species Action Plans, a regional monitoring strategy and further research on the effects on climate change and prey reductions. OSPAR recommends creating a network of hunting-free reserves in coastal areas. Monitoring of bycatch of this species through on board observer programmes is needed, and appropriate mitigation measures implemented where necessary. Sustainably manage fisheries to prevent over-fishing.
Text account compilers
Ashpole, J, Butchart, S., Calvert, R., Ekstrom, J., Malpas, L.
BirdLife International (2017) Species factsheet: Rissa tridactyla. Downloaded from http://www.birdlife.org on 19/10/2017. Recommended citation for factsheets for more than one species: BirdLife International (2017) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 19/10/2017.