Justification 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.

Family/Sub-family Gaviidae

Species name author (Brünnich, 1764)

Taxonomic source(s) AERC TAC (2003), AOU checklist (1998 + supplements), Cramp and Simmons (1977-1994), Sibley and Monroe (1990, 1993), Stotz et al. (1996)

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

610,000 - 640,000

unset

18,700,000 km²

No

Important Bird Areas Click here to view map showing IBAs where species is recorded and triggers any of the IBA criteria.

Ecology: Behaviour This species is strongly migratory, with inland breeding populations moving south or to the coast after breeding¹. The species breeds from May onwards in isolated solitary pairs, nesting later further to the north depending on the timing of the thaw¹. Adults become flightless for a short time in late-winter when they moult their flight feathers³. During the winter the species occurs singly, in pairs or in small loose flocks in marine habitats^{2, 3}, occasionally also forming large congregations of c.300^{1, 3}. Habitat Breeding The species breeds on large, deep freshwater lakes in coniferous forest or on open tundra¹, requiring clear water with visibilities of at least 3-4 m and small islands (less than 2.5 ha) for nesting⁷. Non-breeding It winters along the coast on exposed rocky shores, sheltered bays¹, channels and sheltered inlets² showing a preference for shallow inshore waters⁷. It may also be found inland¹ on lakes and reservoirs during this season², although this is largely influenced by the weather⁷. Diet Its diet consists predominantly of fish as well as crustaceans, molluscs, aquatic insects, annelid worms, frogs, other amphibians and plant matter (e.g. Potamogeton spp., willow Salix spp. shoots, roots, seeds, moss and algae)¹. Breeding site The nest is a mound of plant matter screened by vegetation² and placed near the water's edge¹ on islands, islets or promontories². Management information There is evidence that introducing floating nesting platforms on lakes is successful in increasing the reproductive success of the species^5, 7, and that nest losses caused by flooding can be reduced by controlling water levels during the nesting period⁷. Mortality from entanglement and drowning in fishing nets could also be reduced by using fish traps with openings at the top to allow birds to escape, or by checking traps more regularly for captured birds⁷.

Threats When breeding the species is threatened by fluctuating water levels¹ (e.g. due to the building of dams)⁷, acidification of breeding lakes^{1, 5,} 7, heavy metal pollution^{1, 7} (e.g. methylmercury contamination)⁵ and lead poisoning from ingested lead fishing weights^{4, 6}. It is also highly sensitive to human disturbance¹ such as shoreline development and human recreation^5, 7, and may desert lakes after increases in human presence and activities¹. During the winter the species is highly vulnerable to coastal oil spills, especially in areas where large congregations form¹, and entanglement in monofilament fishing lines (used for sport fishing) and commercial fishing nets causes significant mortality at sea and on larger lakes^{1, 7}. The species is also susceptible to avian botulism so may be threatened by future outbreaks of the disease^{1, 7}.

References 1. del Hoyo et al (1992). 2. Snow and Perrins (1998). 3. Godfrey (1979). 4. Sidor et al. (2003). 5. Piper et al. (2002). 6. Scheuhammer et al. (2003). 7. Rimmer (1992).

Further web sources of information

Detailed species account from Birds in Europe: population estimates, trends and conservation status (BirdLife International 2004)

Text account compilers Stuart Butchart (BirdLife International), Jonathan Ekstrom (BirdLife International), Lucy Malpas (BirdLife International)

IUCN Red List evaluators Jeremy Bird (BirdLife International), Stuart Butchart (BirdLife International)

Recommended citation BirdLife International (2009) Species factsheet: Gavia immer. Downloaded from http://www.birdlife.org on 9/2/2010

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

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