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LC
Gadwall Mareca strepera

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). The population trend is not known, but the population is not believed to be decreasing sufficiently rapidly to approach the thresholds 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.

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.

Taxonomic note
Mareca strepera (del Hoyo and Collar 2014) was previously placed in the genus Anas.

Synonym(s)
Anas strepera Linnaeus, 1758

Distribution and population
Anas strepera has an extremely wide distribution across the Palearctic and Nearctic regions, occurring in the U.S.A., Canada, Mexico, Guatemala, Belize, Cuba, Jamaica, Iceland, Ireland, the United Kingdom, Portugal, Spain, Morocco, Western Sahara, Andorra, France, Monaco, Belgium, Luxembourg, the Netherlands, Switzerland, Liechtenstein, Austria, Italy, Germany, Denmark, the Czech Republic, Slovenia, Croatia, Bosnia and Herzegovina, Serbia, Montenegro, Kosovo, Albania, The Former Yugoslav Republic of Macedonia, Greece, Bulgaria, Romania, Hungary, Slovakia, Moldova, Ukraine, Belarus, Russia, Turkey, Tunisia, Libya, Egypt, Sudan, Ethiopia, Georgia, Armenia, Azerbaijan, Syria, Israel, Lebanon, Jordan, Iraq, Saudi Arabia, Iran, Turkmenistan, Uzbekistan, Tajikistan, Kyrgyzstan, China, Mongolia, Pakistan, India, Nepal, Bangladesh, Bhutan, Burma and Japan. The subspecies couesi was discovered on Teraina, Kiribati in 1874, but it has not been seen since and is now extinct (del Hoyo et al. 1992).

Population justification
The global population is estimated to number c.3,200,000-3,800,000 individuals (Wetlands International 2006), while national population estimates include: c.100-10,000 breeding pairs and c.50-1,000 wintering individuals in China; c.1,000-10,000 wintering individuals in Korea and <c.100 breeding pairs and c.50-1,000 wintering individuals in Japan (Brazil 2009).

Trend justification
The overall population trend is uncertain, as some populations are decreasing, while others are stable, have unknown trends or are increasing (Wetlands International 2006). This species has undergone a large and statistically significant increase over the last 40 years in North America (506% increase over 40 years, equating to a 56.9% increase per decade; data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007).

Ecology
Behaviour The species is strongly migratory in the north of its range (Kear 2005b) although breeding populations in temperate regions are largely sedentary (del Hoyo et al. 1992). Males leave the breeding grounds in early-July (one month before the females and young), migrating to key waters to undergo a flightless moulting period lasting for c.4 weeks, after which they continue to the wintering grounds (Scott and Rose 1996). The return migration occurs from March to April (Scott and Rose 1996), and although the timing of the breeding season varies geographically the species generally nests late in the year (e.g. May-July) (Kear 2005b). It breeds in single pairs or loose groups (del Hoyo et al. 1992) and is usually observed in small parties outside of the breeding season, with large concentrations sometimes forming on passage (Madge and Burn 1988) or during the moulting period (Kear 2005b) (Madge and Burn 1988). Habitat The species inhabits highly productive (del Hoyo et al. 1992, Kear 2005b) and eutrophic (Snow and Perrins 1998) freshwater marsh or lake habitats (del Hoyo et al. 1992, Kear 2005b) in open lowland grassland (Johnsgard 1978, Madge and Burn 1988), showing a preference for sheltered, shallow, standing or slow-flowing waters (Snow and Perrins 1998) with abundant emergent vegetation (Johnsgard 1978, del Hoyo et al. 1992, Snow and Perrins 1998, Kear 2005b) and grass-covered islands providing cover for nesting (Johnsgard 1978, del Hoyo et al. 1992, Snow and Perrins 1998). It may also be found on permanent, shallow, slightly alkaline marshes (Johnsgard 1978, del Hoyo et al. 1992), as well as on oxbow lakes, channels (Flint et al. 1984), reservoirs and gravel-pits (Kear 2005b). After hatching, females move their broods to deeper marshes or to the edges of large impoundments, sometimes more than 1 mile away from the nesting sites (Johnsgard 1978). Rarely (e.g. in the winter) (Madge and Burn 1988) the species occurs along sheltered coasts (del Hoyo et al. 1992, Scott and Rose 1996) at coastal marshes (North America) (Kear 2005b), estuaries (Flint et al. 1984, Madge and Burn 1988, Snow and Perrins 1998), deltas or lagoons (Snow and Perrins 1998). Diet The species is predominantly herbivorous (del Hoyo et al. 1992), its diet consisting of the seeds, leaves, roots and stems of aquatic plants (del Hoyo et al. 1992) (submerged and emergent) as well as grasses and stoneworts Chara spp. (Kear 2005b), occasionally also taking cereal grains on land (Brown et al. 1982, Snow and Perrins 1998). In addition, the species may take a small amount of animal matter during the winter (Africa), such as insects, molluscs, annelids, amphibians, amphibian spawn and small fish (Brown et al. 1982). Breeding site The nest is a well-hidden (Johnsgard 1978) hollow (Snow and Perrins 1998) in grass and leaves positioned on the ground in thick vegetation (del Hoyo et al. 1992) such as nettles Urtica spp. (Madge and Burn 1988), grass tussocks, thick bushes, rushes or tall grass (Brown et al. 1982). The species shows a preference for dense, dry herbaceous vegetation (Johnsgard 1978) and often nests far from water (Madge and Burn 1988, Kear 2005b). It may nest in dense concentrations on islands (Madge and Burn 1988, Kear 2005b) (neighbouring nests as close as 5 m apart) (Snow and Perrins 1998) although it is not a colonial species (Madge and Burn 1988, Kear 2005b). Management information The cyclical removal of adult fish from an artificial waterbody (gravel pit) in the UK (leaving small fish for piscivorous birds) resulted in an increase in the winter use of the habitat by the species as result of an increase in the growth of submerged aquatic macrophytes (Giles 1994). The removed fish (dead or alive) were sold to generate funds (Giles 1994).

Threats
The species is threatened by pollution (Kear 2005b) and disturbance from recreational use of freshwater wetlands (Kear 2005b, Pease et al. 2005). It also suffers mortality as a result of lead shot ingestion (Spain) (Mondain-Monval et al. 2002) and nest predation by American mink Neovison vison (Europe) (Opermanis et al. 2001). The species is susceptible to avian influenza, so may be threatened by future outbreaks (Melville and Shortridge 2006). Utilisation The species is hunted throughout most of its range (Kear 2005b) both for recreation (Bregnballe et al. 2006, Shortridge et al. 2006) and commercial uses (Balmaki and Barati 2006), but is rarely taken in large numbers except where it is particularly abundant (Kear 2005b). The eggs of this species used to be (and possibly still are) harvested in Iceland (Gudmundsson 1979).

References
Balmaki, B.; Barati, A. 2006. Harvesting status of migratory waterfowl in northern Iran: a case study from Gilan Province. In: Boere, G.; Galbraith, C., Stroud, D. (ed.), Waterbirds around the world, pp. 868-869. The Stationary Office, Edinburgh, UK.

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

Bregnballe, T.; Noer, H.; Christensen, T. K.; Clausen, P.; Asferg, T.; Fox, A. D.; Delany, S. 2006. Sustainable hunting of migratory waterbirds: the Danish approach. In: Boere, G.; Galbraith, C., Stroud, D. (ed.), Waterbirds around the world, pp. 854-860. The Stationary Office, Edinburgh, UK.

Brown, L. H.; Urban, E. K.; Newman, K. 1982. The birds of Africa vol I. Academic Press, 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.

Flint, V. E.; Boehme, R. L.; Kostin, Y. V.; Kuznetsov, A. A. 1984. A field guide to birds of the USSR. Princeton University Press, Princeton, New Jersey.

Giles, N. 1994. Tufted Duck (Aythya fuligula) habitat use and brood survival increases after fish removal from gravel pit lakes. Hydrobiologia 279/280: 387-392.

Gudmundsson, F. 1979. The past status and exploitation of the Myvatn waterfowl populations. Oikos 32((1-2)): 232-249.

Johnsgard, P. A. 1978. Ducks, geese and swans of the World. University of Nebraska Press, Lincoln and London.

Kear, J. 2005. Ducks, geese and swans volume 2: species accounts (Cairina to Mergus). Oxford University Press, Oxford, U.K.

Madge, S.; Burn, H. 1988. Wildfowl. Christopher Helm, London.

Melville, D. S.; Shortridge, K. F. 2006. Migratory waterbirds and avian influenza in the East Asian-Australasian Flyway with particular reference to the 2003-2004 H5N1 outbreak. In: Boere, G.; Galbraith, C., Stroud, D. (ed.), Waterbirds around the world, pp. 432-438. The Stationary Office, Edinburgh, UK.

Mondain-Monval, J. Y.; Desnouhes, L.; Taris, J. P. 2002. Lead shot ingestion in waterbirds in the Camargue, (France). Game and Wildlife Science 19(3): 237-246.

Murphy-Klassen, H. M.; Underwood, T. J.; Sealy, S. G.; Czyrny, A. A. 2005. Long-term trends in spring arrival dates of migrant birds at Delta Marsh, Manitoba, in relation to climate change. The Auk 122: 1130-1148.

Opermanis, O.; Mednis, A.; Bauga, I. 2001. Duck nests and predators: interaction, specialisation and possible management. Wildlife Biology 7(2): 87-96.

Pease, M. L.; Rose, R. K.; Butler, M. J. 2005. Effects of human disturbances on the behavior of wintering ducks. Wildlife Society Bulletin 33(1): 103-112.

Scott, D. A.; Rose, P. M. 1996. Atlas of Anatidae populations in Africa and western Eurasia. Wetlands International, Wageningen, Netherlands.

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

View photos and videos and hear sounds of this species from the Internet Bird Collection

Text account compilers
Butchart, S., Ekstrom, J., Khwaja, N., Malpas, L.

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

Recommended citation
BirdLife International (2014) Species factsheet: Mareca strepera. Downloaded from http://www.birdlife.org on 27/08/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 27/08/2014.

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.

Key facts
Current IUCN Red List category Least Concern
Family Anatidae (Ducks, Geese, Swans)
Species name author Linnaeus, 1758
Population size mature individuals
Population trend Unknown
Distribution size (breeding/resident) 17,400,000 km2
Country endemic? No
Links to further information
- Additional Information on this species