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LC
Horned Grebe Podiceps auritus

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.

Taxonomic source(s)
AERC TAC. 2003. AERC TAC Checklist of bird taxa occurring in Western Palearctic region, 15th Draft. Available at: #http://www.aerc.eu/DOCS/Bird_taxa_of _the_WP15.xls#.
Cramp, S.; Perrins, C. M. 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.
del Hoyo, J.; Collar, N. J.; Christie, D. A.; Elliott, A.; Fishpool, L. D. C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Barcelona, Spain and Cambridge UK: Lynx Edicions and BirdLife International.

Distribution and population
Podiceps auritus can be found across from Iceland, northern United Kingdom and Scandinavia in Europe, and throughout the centre of Russia to the Pacific coast. It also breeds in southern Alaska (USA), in most of western and central Canada, and in northern USA. Wintering grounds occur further south, including the North Sea, Adriatic Sea, Black Sea and the Caspian Sea, as well as the coast Japan, Korea and China, and the USA down to California on the Pacific coast and Texas on the Atlantic coast (del Hoyo et al. 1992).

Population justification
The global population is estimated to number c.140,000-1,100,000 individuals (Wetlands International 2006), while national population sizes have been estimated at c.50-1,000 individuals on migration and < c.50 wintering individuals in China and c.100-100,000 breeding pairs and c.50-10,000 individuals on migration in Russia (Brazil 2009).

Trend justification
The overall population trend is decreasing, although some populations may be stable and others have unknown trends (Wetlands International 2006). This species has undergone a large and statistically significant decrease over the last 40 years in North America (-75.9% decline over 40 years, equating to a -29.9% decline per decade; data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007).

Ecology
Behaviour This species is fully migratory (del Hoyo et al. 1992) and travels over land in stages on a broad front, some populations only moving short distances to the nearest ice-free coast (Fjeldsa 2004). The species breeds from April to August (del Hoyo et al. 1992) in solitary isolated pairs (del Hoyo et al. 1992, Fjeldsa 2004), small loose colonies occasionally forming on lakes with rich extensive feeding areas (Fjeldsa 2004). During the non-breeding season the species usually remains solitary or forages in pairs or small groups (Snow and Perrins 1998) although flocks of up to c.500 individuals may gather occasionally on the sea during the winter (Fjeldsa 2004) and flocks of up to 60 individuals may travel together on passage (Snow and Perrins 1998). Habitat Breeding The species breeds on small, shallow fresh (del Hoyo et al. 1992), brackish or slightly alkaline (Fjeldsa 2004) waters between 0.5 and 2 m deep and between 1 and 20 ha in area (Snow and Perrins 1998) with rich floating (Konter 2001), submergent and emergent vegetation (Fjeldsa 2004). Habitats include small pools, marshes with patches of open water and secluded sections of larger lakes and rivers (del Hoyo et al. 1992). Non-breeding In its wintering range the species frequents coastal inshore waters (del Hoyo et al. 1992) up to 10-20 m in depth (Fjeldsa 2004) including sheltered bays (del Hoyo et al. 1992), lagoons and estuaries (Ogilvie and Rose 2003). It may also occur on large lake and river systems south of its breeding range (del Hoyo et al. 1992, Fjeldsa 2004). Diet Its diet consists predominantly of fish and invertebrates such as adult and larval insects (e.g. beetles, dragonflies, mayflies, water bugs, damselflies and caddisflies), crustaceans (del Hoyo et al. 1992) (e.g. brine shrimp, cladocerans, amphipods, decapods (del Hoyo et al. 1992), crayfish (Fjeldsa 2004) and crabs (Konter 2001)), molluscs and worms (del Hoyo et al. 1992). Fish and crustaceans are more important components of the diet during the winter when the species is at sea (del Hoyo et al. 1992). Breeding site The nest is a platform of aquatic vegetation either floating and anchored to emergent vegetation, built from the lake bottom (where water is shallow) or built on rocks at water level (del Hoyo et al. 1992). Management information At a breeding lake in Scotland (Loch Ruthven) sedge beds are being extended to provide more nesting habitat for the species (Ogilvie and Rose 2003).

Threats
The main threats to the species are human disturbance, forestry operations around breeding lakes (e.g. afforestation leading to hydrological changes and resulting in reduced numbers of invertebrate prey), fluctuating water levels, and the stocking of lakes with rainbow trout Salmo gairdneri (which competes with the species for aquatic insects) (del Hoyo et al. 1992). Historical range contractions have also occurred due to acidification and increased humus content of lakes, and the species is vulnerable to hypertrophication (Fjeldsa 2004). It is commonly caught and accidentally drowning in fishing nets (del Hoyo et al. 1992) and is particularly vulnerable to oil spills in the marine environment during the winter (del Hoyo et al. 1992, Ogilvie and Rose 2003, Fjeldsa 2004).

References
Brazil, M. 2009. Birds of East Asia: eastern China, Taiwan, Korea, Japan, eastern Russia. Christopher Helm, London.

del Hoyo, J.; Elliot, A.; Sargatal, J. 1992. Handbook of the Birds of the World, vol. 1: Ostrich to Ducks. Lynx Edicions, Barcelona, Spain.

Delany, S.; Scott, D. 2006. Waterbird population estimates. Wetlands International, Wageningen, The Netherlands.

Fjeldså, J. 2004. The grebes. Oxford University Press, Oxford, U.K.

Konter, A. 2001. Grebes of our world. Lynx Edicions, Barcelona.

Ogilvie, M.; Rose, C. 2003. Grebes of the World. Bruce Coleman, Uxbridge.

Snow, D. W.; Perrins, C. M. 1998. The Birds of the Western Palearctic vol. 1: Non-Passerines. Oxford University Press, Oxford.

Further web sources of information
Detailed species account from Birds in Europe: population estimates trends and conservation status (BirdLife International 2004)

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

Explore HBW Alive for further information on this species

Search for photos and videos, and hear sounds of this species from the Internet Bird Collection

Text account compilers
Ekstrom, J., Butchart, S., Malpas, L., Calvert, R.

IUCN Red List evaluators
Butchart, S., Symes, A.

Recommended citation
BirdLife International (2014) Species factsheet: Podiceps auritus. Downloaded from http://www.birdlife.org on 24/10/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 24/10/2014.

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

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

ARKive species - Horned grebe (Podiceps auritus)

Key facts
Current IUCN Red List category Least Concern
Family Podicipedidae (Grebes)
Species name author (Linnaeus, 1758)
Population size mature individuals
Population trend Decreasing
Distribution size (breeding/resident) 4,000,000 km2
Country endemic? No
Links to further information
- Additional Information on this species