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 increasing, 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 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.18,000,000 individuals (del Hoyo et al. 1996). The European population is estimated at 2,350,000-3,060,000 mature individuals (BirdLife International 2015).
The population trend is increasing in North America (based on BBS/CBC data: Butcher and Niven 2007). Although a number of populations are increasing, including in the UK (which holds nearly half the European population) since 2000 (JNCC 2014), a recent sharp decline was observed in Iceland (where nearly a quarter of the European population is found) since 2005. As a result of the reported decline in Iceland, the estimated and projected rate of decline of the European population size over the period 2005-2050 (three generations) varies from 25% to more than 50% (BirdLife International 2015).
This species has a circumpolar distribution, occuring in the low-arctic and boreal waters of the north Atlantic and north Pacific (del Hoyo et al. 1996).
Behaviour The Common Guillemot is a pursuit-diving marine bird which forages primarily during daylight. One parent remains at the colony with the chick whilst the other is on a foraging trip. Birds departing colonies usually splash-down to form large rafts close to the colony before departing to foraging areas. External radio tagging has been shown to adversely effect breeding (Wanless et al. 1988, Nevins 2004), whereas birds fitted with internal transmitters behaved as normal (Wanless et al. 1988). Diet During the breeding season, schooling pelagic fish species are the most important prey for adults, though benthic species can also be important.In Labrador, Canada, Shannies (Sticheaidae) were the main source of food, comprising 84% of the diet in 1996 and 52.9% in 1997 (Bryant and Jones 1999). Capelin (Mallotus villosus) were also important, forming 44.7% of the diet in 1997 (Bryant and Jones 1999). In the UK, the main prey taxa are sandeel (Ammodytes spp.) and clupeids. Small gadoids are also important at some colonies. Foraging range This species dives to maximum depths of 170-230m. During the breeding season, surveys recorded the highest densities of birds in the 51 - 100 m depth zone, although birds were still abundant in water less than 50 m and 101 - 200 m deep. Very few were seen in deeper areas (Wanless et al. 1990). The foraging range of this species appears variable across seasons and years. At the Isle of May, Scotland, during 1986 around 70% of foraging trips were over 7 km from the colony, whereas in the following year the birds tended to make shorter trips (Wanless et al. 1990). Foraging trips in eastern Canada are within 100 km (Cairns et al. 1987, Davoren et al. 2003), and in Pribilof Islands, Alaska, foraging occurred mostly within 60 km. In Witless Bay, Newfoundland, foraging aggregations formed over large Capelin schools within 5 km of breeding sites. Along the Newfoundland coastline, aggregations occurred within 15 km of the colonies, and at an offshore ridge about 80 km southeast of the colonies. Despite these large foraging radii, waters close to the colony were the most frequent destination of feeding birds. This was particularly true during chick rearing, when only one third of feeding trips could have exceeded 10 km from the colony (Cairns et al. 1987). In Pribilof Islands, Alaska, birds showed a consistent preference for shallower waters (Schneider and Hunt 1984). High densities of foraging birds have also been observed foraging over a submarine ridge (Coyle et al. 1992). In Kachemak Bay, Alaska, it appears that birds tend to feed over rocky substrates in water depths of about 18 to 55 m (Sanger 1987). They have also been observed to forage in riptides (Wanless et al. 1990), and in areas of sandy sediment suitable for sandeels (Wanless et al. 1998, BirdLife International 2000). Near Flamborough Head, UK, the Farallones, California, and Pribilof Islands, Alaska, birds forage at fronts between thermally distinct bodies of water. In the UK example, this occurs at a seasonally-occuring front between thermally-mixed and thermally-stratified water, whereas in the Farallones, the front was between cold and salty upwellings and estuarine outflow (Decker and Hunt 1996, BirdLife International 2000).
This species is highly vulnerable to human disturbance as it is found in high concentrations outside the breeding season. Throughout the 19th and early 20th centuries, egg collection and shooting at colonies, as well as introduced alien predators caused severe declines in the world population and unregulated hunting in Greenland, the Faeroes and Newfoundland is still a major threat. As human populations increased and expanded the species was extirpated in many regions, particularly in the south of its range.
Other important threats are overfishing of important forage species (e.g. capelin, herring, cod and sandeels) in the North Atlantic (Barents Sea, Iceland, east Newfoundland and Grand Banks, Scotian Shelf and Gulf of Maine) and North Pacific and uncontrolled gill-net fisheries in the north-east Atlantic and north Pacific. As well as oil pollution and offshore petroleum developments in both the Atlantic and Pacific Oceans, including areas such as the Barents and North Seas, Greenland, east Newfoundland and Grand Banks and Alaska south to California (Nettleship et al. 2016). The species is susceptible to avian cholera (Österblom et al. 2004) so is threatened by future outbreaks of this disease. Wind farm development has a negative impact on this species as well (Vanermen et al. 2014). The species is also likely threatened by future climate change (Sandvik 2005, Frederiksen et al. 2013).
Conservation Actions Underway
Uria aalge ibericus is found on Annex I of the EU Birds Directive. With the implementation of bird protection laws, a slow recovery occurred over much of the Atlantic breeding range up to the early 1970s except in north Norway and probably Iceland (Nettleship et al. 2016).
Conservation Actions Proposed
At major colonies, detailed monitoring is needed, particularly in Iceland, where the status of the largest Atlantic population is poorly known (Nettleship et al. 2016). The impact of bycatch in fish nets can be reduced in several ways: Protecting areas on a seasonal and/or diurnal scale; concentrating salmon fisheries when salmon densities are high to improve fishing efficiency and catch to bycatch ratios; changing to an alternative fishing technique may reduce seabird mortality; and gear modification (Österblom et al 2002).
Text account compilers
Ashpole, J, Butchart, S., Calvert, R., Ekstrom, J., Hatchett, J.
BirdLife International (2018) Species factsheet: Uria aalge. Downloaded from http://www.birdlife.org on 19/08/2018. Recommended citation for factsheets for more than one species: BirdLife International (2018) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 19/08/2018.