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 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 to number c.200,000-600,000 individuals (Wetlands International 2015), while national population estimates include: c.50-10,000 wintering individuals in Japan and c.10,000-100,000 breeding pairs and c.1,000-10,000 wintering individuals in Russia (Brazil 2009). The European population is estimated at 42,100-93,000 pairs, which equates to 84,200-186,000 mature individuals (BirdLife International 2015).
The overall population trend is decreasing, although some populations may be stable and others have unknown trends (Wetlands International 2015). This species has had stable population trends over the last 40 years in North America (data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007). The European population trend is unknown (BirdLife International 2015).
The species is migratory, breeding in the Arctic Regions of the northern hemisphere generally north of 50°, and wintering along the Pacific and Atlantic coasts of North America as far south as Florida and California (U.S.A.), on the coast of Portugal, in the Mediterranean Sea and Black Sea, and on the Pacific coast of Asia as far south as south-east China.
Behaviour This species is strongly migratory, with inland populations moving south or to the coast after breeding (del Hoyo et al. 1992). The species breeds from May onwards, nesting later further to the north depending on the timing of the thaw (del Hoyo et al. 1992). It usually nests solitarily on smaller waters but may nest in loosely colonial groups on larger waters (e.g. several pairs nesting a few metres apart on the same lake) (Snow and Perrins 1998). On migration, large flocks of 200-1,200 individuals may form, with similar concentrations occurring on rich marine fishing grounds during the winter (del Hoyo et al. 1992). The species is most commonly observed singly, in pairs or in small scattered flocks during this season however (Snow and Perrins 1998). Habitat Breeding The species breeds on freshwater pools or lakes in open moorland, blanket bogs or open and wet peatland habitats (Campbell 1987, del Hoyo et al. 1992). It will nest on pools as small as 10-20 m long or on lakes up to 5 ha in area, showing a preference for those in treeless areas that have well-vegetated margins and low islets or promontories on which to nest (Snow and Perrins 1998). It generally avoids waters with dense floating or emergent vegetation and steep rocks above the water, and if feeding conditions are inadequate in the pool chosen for breeding the species may fly to the coast or to lakes with higher abundances of fish in order to feed (Snow and Perrins 1998). Non-breeding Outside of the breeding season, the species frequents inshore waters along sheltered coasts, occasionally occurring inland on lakes, pools, reservoirs and rivers (del Hoyo et al. 1992, Snow and Perrins 1998). Diet Its diet consists predominantly of fish as well as crustaceans, molluscs, frogs, fish spawn, aquatic insects, annelid worms and plant matter (del Hoyo et al. 1992, Snow and Perrins 1998). Breeding site The nest is a small depression or a mound of plant matter, built in shallow water up to 10 m from the shore or very near the water's edge, on islets or small promontories (Flint et al. 1984, del Hoyo et al. 1992, Snow and Perrins 1998). Nesting pairs will often re-use the same site in successive years (Snow and Perrins 1998).
Highly vulnerable to oil spills, especially in wintering areas where large concentrations form (e.g. on rich fishing grounds) (del Hoyo et al. 1992). Climate change is likely to result in a large shift in the North American summer range, possibly resulting in a decrease in the amount of suitable habitat. The Red-throated Loon has been found to be frequently caught as bycatch in studies in the Baltic (Schirmeister 2003, Zydelis et al. 2013) and in the northwest Atlantic (Warden 2010). A small study in the German Baltic found 370 drowned birds over 12 winters (HELCOM 2013). This species also has a strong reaction to disturbance from ships and helicopters, resulting in an altered population distribution and habitat fragmentation. It is considered to be a species at relatively high risk of collision with wind turbines and other offshore infrastructure due to nocturnal flight behaviour and low manoeuvrability (Garthe and Hüppop 2004).
Conservation Actions Underway
The species is listed on Annex II of the Convention on Migratory Species, and is listed under the African Eurasian Waterbird Agreement. It is listed on Annex II of the Bern Convention, Annex I of the EU Birds Directive and listed as critically endangered on the HELCOM convention. The following information refers to the species's European range only: There are 58 Important Bird and Biodiversity Areas for this species. Within the EU it occurs and is protected in 426 Special Protection Areas. Since the 1970s, conservation work in Finland has included building artificial rafts for this species to reduce predation risk, which has led to higher breeding success in some areas. Within the North Sea (Germany), work is underway to test alternative fishing gears to gillnets, while in Lithuania gill-net bycatch mitigation is being trialled. In Scotland, attempts have been made to implement education schemes for fishermen and land-owners to try to reduce disturbance and mortality of the species on breeding lakes (Campbell 1987).
Conservation Actions Proposed
The following information refers to the species's European range only: Development of mitigation measures for gillnet bycatch for commercial and artisanal fishing vessels. Prevention of chronic oil pollution and oil spill events, and development of rapid, trans-boundary plans for oil spill response. Protection of feeding grounds, and regulations for vessel traffic, management of recreational activities at important breeding and non-breeding sites, careful siting of windfarms away from critical habitat or migration pathways. The introduction of floating artificial nesting rafts may also be successful in increasing the species's breeding success (Campbell 1987).
Text account compilers
Stuart, A., Ekstrom, J., Ashpole, J, Fjagesund, T., Calvert, R., Hermes, C., Hibble, R., Butchart, S., Malpas, L.
BirdLife International (2019) Species factsheet: Gavia stellata. Downloaded from http://www.birdlife.org on 21/10/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 21/10/2019.