Mergus serrator 

Scope: Global
Language: English

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Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Anseriformes Anatidae

Scientific Name: Mergus serrator Linnaeus, 1758
Regional Assessments:
Common Name(s):
English Red-breasted Merganser
Taxonomic Source(s): Cramp, S. and Simmons, K.E.L. (eds). 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2016
Date Assessed: 2016-10-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Contributor(s): Pihl, S.
Facilitator/Compiler(s): Ashpole, J, Butchart, S., Calvert, R., Ekstrom, J., Malpas, L.
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 stable, 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 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.
Previously published Red List assessments:

Geographic Range [top]

Range Description:This species breeds in most of the northern North America, south to the Great Lakes, in Greenland (to Denmark), Iceland, and much of northern Eurasia south to the United Kingdom, parts of Eastern Europe, north-east China and northern Japan. Its wintering grounds expand its range to include the Atlantic and Pacific coasts of North America, areas of central Europe and the Mediterranean basement, the Black Sea, the southern Caspian Sea, the southern coast of Iran and Pakistan, the eastern coast of China, and the coasts of Korea and Japan (del Hoyo et al. 1992).

Countries occurrence:
Albania; Armenia; Austria; Azerbaijan; Bahamas; Belarus; Belgium; Bermuda; Bosnia and Herzegovina; Bulgaria; Canada; China; Croatia; Cuba; Cyprus; Czech Republic; Denmark; Egypt; Estonia; Faroe Islands; Finland; France; Germany; Greece; Greenland; Hungary; Iceland; Iran, Islamic Republic of; Iraq; Ireland; Israel; Italy; Japan; Kazakhstan; Korea, Democratic People's Republic of; Korea, Republic of; Kyrgyzstan; Latvia; Libya; Liechtenstein; Lithuania; Macedonia, the former Yugoslav Republic of; Malta; Mexico; Moldova; Montenegro; Morocco; Netherlands; Norway; Pakistan; Poland; Portugal; Romania; Russian Federation (Central Asian Russia, Eastern Asian Russia, European Russia); Saint Pierre and Miquelon; Serbia; Slovakia; Slovenia; Spain (Canary Is. - Vagrant); Sweden; Switzerland; Taiwan, Province of China; Tunisia; Turkey; Turkmenistan; Turks and Caicos Islands; Ukraine; United Kingdom; United States; Uzbekistan
Afghanistan; Algeria; Bahrain; Belize; Cayman Islands; Dominican Republic; Gibraltar; Haiti; India; Jordan; Kuwait; Lebanon; Luxembourg; Mongolia; Nepal; Northern Mariana Islands; Oman; Palestinian Territory, Occupied; Puerto Rico; Saudi Arabia; Svalbard and Jan Mayen; Syrian Arab Republic; United Arab Emirates; Virgin Islands, U.S.
Present - origin uncertain:
Additional data:
Continuing decline in area of occupancy (AOO):Unknown
Extreme fluctuations in area of occupancy (AOO):NoEstimated extent of occurrence (EOO) - km2:64900000
Continuing decline in extent of occurrence (EOO):UnknownExtreme fluctuations in extent of occurrence (EOO):No
Continuing decline in number of locations:Unknown
Extreme fluctuations in the number of locations:No
Range Map:Click here to open the map viewer and explore range.

Population [top]

Population:The global population is estimated to number c.495,000-605,000 individuals (Wetlands International 2016). The European population is estimated at 70,100-120,000 pairs, which equates to 140,000-240,000 mature individuals (BirdLife International 2015). National population estimates include: c.100-10,000 breeding pairs and c.50-1,000 wintering individuals in China; c.50-10,000 wintering individuals in Korea and c.100,000-1 million breeding pairs and c.1,000-10,000 wintering individuals in Russia (Brazil 2009).

Trend Justification:  The overall population trend is stable, although some populations have unknown trends (Wetlands International 2016). 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). In Europe the population size is estimated to be decreasing at a rate approaching 30% in 21.9 years (three generations) (BirdLife International 2015).
Current Population Trend:Stable
Additional data:
Continuing decline of mature individuals:Unknown
Extreme fluctuations:NoPopulation severely fragmented:No
Continuing decline in subpopulations:Unknown
Extreme fluctuations in subpopulations:NoAll individuals in one subpopulation:No

Habitat and Ecology [top]

Habitat and Ecology:Behaviour This species is fully migratory (Madge and Burn 1988, del Hoyo et al. 1992) although in temperate regions it only undertakes short distance movements to nearby coasts (Scott and Rose 1996) or remains close to its breeding waters throughout the year (Madge and Burn 1988). It breeds from April or May (later in northern populations) (Kear 2005b) in single pairs or colonies (del Hoyo et al. 1992) on islands or small islets, adults often assembling in groups on beaches when not at the nest (even when nesting solitarily) (Kear 2005b). Males leave the breeding grounds in June to moult in small groups along the coast (Scott and Rose 1996), often considerable distances from the breeding areas (Snow and Perrins 1998) (although there is no evidence for any major migrations to common moulting sites) (Johnsgard 1978). The autumn migration begins in September (Scott and Rose 1996) and the species returns from the wintering grounds as early as February (Scott and Rose 1996). It is gregarious during the winter and on migration (Kear 2005b), flocks of up to a hundred or more occurring in suitable sites during the autumn (although it travels in much smaller flocks during the spring) (Snow and Perrins 1998). Habitat Breeding The species breeds along the wooded shorelines (Kear 2005b) of deep lakes (del Hoyo et al. 1992), small rivers and streams (del Hoyo et al. 1992) with moderate currents (Snow and Perrins 1998) in the tundra, boreal and temperate forest zones (Snow and Perrins 1998, Kear 2005b), as well as on more saline waters such as sheltered shallow bays, inlets, straits or estuaries with sandy rather than muddy substrates (Snow and Perrins 1998). It shows a preference for narrow channels rather than open expanses of water, with islands or islets and spits, projecting rocks or grassy banks (Snow and Perrins 1998). Non-breeding The majority of the species winters at sea (del Hoyo et al. 1992), frequenting both inshore and offshore waters, estuaries, bays and brackish lagoons (del Hoyo et al. 1992) but showing a preference for clear, shallow waters not affected by heavy wave action (Johnsgard 1978). It will also utilise large freshwater lakes on passage (Madge and Burn 1988). Diet Its diet consists predominantly of small, shoaling marine or freshwater fish (del Hoyo et al. 1992), as well as small amounts of plant material (del Hoyo et al. 1992) and aquatic invertebrates (del Hoyo et al. 1992) such as crustaceans (e.g. shrimps and crayfish) (Johnsgard 1978), worms and insects (Kear 2005b). Breeding site The nest is constructed within 25 m of water (Kear 2005b) in a variety of locations such as natural cavities on the ground (Johnsgard 1978, del Hoyo et al. 1992, Kear 2005b) , burrows (del Hoyo et al. 1992, Kear 2005b), under boulders (Madge and Burn 1988), amongst tree or scrub roots (Snow and Perrins 1998), in tree cavities, artificial nestboxes (Madge and Burn 1988), amongst reeds or on floating reed mats (Flint et al. 1984). Where tree cavities or artificial nestboxes are utilised, the species shows a preference for those with entrances c.10 cm in diameter and with internal diameters of 30-40 cm (Johnsgard 1978). Management information The breeding density of this species increased on islands in the outer archipelago of south-west Finland as a result of feral American mink Neovison vison removal (Nordstrom et al. 2002). The species will also nest in artificial nestboxes with entrances c.10 cm in diameter and with internal diameters of 30-40 cm (Johnsgard 1978).
Systems:Terrestrial; Freshwater; Marine
Continuing decline in area, extent and/or quality of habitat:Unknown
Generation Length (years):7.3
Movement patterns:Full Migrant
Congregatory:Congregatory (and dispersive)

Threats [top]

Major Threat(s): The species is subject to persecution and may be shot (Kear 2005b) by anglers and fish-farmers who accuse it of depleting fish stocks (del Hoyo et al. 1992, Kear 2005b). It is also threatened by accidental entanglement and drowning in fishing nets (Kear 2005b). Alterations to its breeding habitats by dam construction and deforestation, and habitat degradation from water pollution are other major threats to the species (del Hoyo et al. 1992). It is also susceptible to avian influenza so may the threatened by future outbreaks of the virus (Melville and Shortridge 2006). Utilisation The species is hunted in North America (Kear 2005b) and Denmark (Bregnballe et al. 2006), although it may not be a popular game species (Kear 2005b). The eggs of the species also used to be (and possibly still are) harvested in Iceland (Gudmundsson 1979).

Conservation Actions [top]

Conservation Actions: Conservation Actions Underway
CMS Appendix II. EU Birds Directive Annex II. The breeding density of this species increased on islands in the outer archipelago of south-west Finland as a result of feral American Mink (Neovison vison) removal (Nordstrom et al. 2002).

Conservation Actions Proposed
The erection of nest boxes may encourage the use of local areas by this species. Strict legislation on petroleum drilling and transport should be enforced and measures to reduce bycatch implemented and enforced. Important areas should be protected from drainage and other habitat modifications. Research into the impact this species has on fish stocks and ways to minimise conflict should be established.

Citation: BirdLife International. 2016. Mergus serrator. The IUCN Red List of Threatened Species 2016: e.T22680485A89372307. . Downloaded on 20 June 2018.
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