Data Zone
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). The population trend appears to be increasing 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 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.
Population justification
The global population is estimated to number c.4,300,000-4,900,000 individuals (Wetlands International 2015). The European population is estimated at 75,400-125,000 pairs, which equates to 151,000-250,000 mature individuals (BirdLife International 2015).
Trend justification
The overall population trend is increasing however some populations are decreasing, while others have unknown trends (Wetlands International 2015). 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). The European population is estimated to be increasing (BirdLife International 2015).
This species 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).
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).
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).
Conservation Actions Underway
CMS Appendix II. EU Birds Directive Annex II. The following information refers to the species's European range only: The cyclical removal of adult fish from an artificial waterbody (gravel pit) in the U.K. (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).
Conservation Actions Proposed
The following information refers to the species's European range only: Important wetland sites should be protected to minimise degradation and disturbance. Appropriate predator control should be undertaken in breeding areas. The impact of hunting should be researched and monitored to ensure bag numbers are sustainable and the use of lead shot banned.
Text account compilers
Butchart, S., Ekstrom, J., Khwaja, N., Malpas, L., Ashpole, J
Recommended citation
BirdLife International (2024) Species factsheet: Gadwall Mareca strepera. Downloaded from
https://datazone.birdlife.org/species/factsheet/gadwall-mareca-strepera on 23/11/2024.
Recommended citation for factsheets for more than one species: BirdLife International (2024) IUCN Red List for birds. Downloaded from
https://datazone.birdlife.org/species/search on 23/11/2024.