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). 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.
The overall trend is decreasing, although some populations may be stable (Wetlands International 2006).
Behaviour This species is mostly sedentary or nomadic, but may disperse long distances (up to 1,800 km) in the dry season depending on the extent of flooding (del Hoyo, et al. 1992, Scott and Rose 1996) (birds ringed in South Africa have been recovered in Namibia. Angola, Zambia and Mozambique) (Scott and Rose 1996). It is a highly social and gregarious species in the non-breeding season, and towards the end of the dry season or at the start of the rains (del Hoyo, et al. 1992) flock sizes can reach several thousand (Madge and Burn 1988) (one flock was estimated at 500,000 on Lake Ngami, Botswana). The species breeds dispersed in single pairs (Madge and Burn 1988), and in southern Africa breeding takes place between December and April (Scott and Rose 1996). In the dry season after the young have hatched, adult birds go through a flightless wing moult that lasts 24-28 days (Johnsgard 1978). The species is largely nocturnal during the rainy season, but at low flood levels birds take aquatic invertebrates by day and graze on aquatic vegetation by night (Brown, et al. 1982). Habitat The species shows a preferences for shallow, still, freshwater habitats with large amounts of submerged, floating, emergent and peripheral vegetation (Johnsgard 1978, del Hoyo, et al. 1992). Suitable habitats vary from lakes to marshes, small rivers (in Madagascar) (Kear 2005b), seasonal pools (ephemeral pans and dams) (Hockey, et al. 2005), farm ponds, large dams (if food is available) (Woodall 1983) and temporarily flooded fields (Johnsgard 1978, del Hoyo, et al. 1992). This species also grazes on land in fields of rice or other crops, especially in fields of stubble (Johnsgard 1978, del Hoyo, et al. 1992). During the dry season the species regularly occurs in small numbers at scattered pans in semi-arid regions (Scott and Rose 1996), although whilst undergoing the dry season flightless moult the species favours large open bodies of water and emergent vegetation (Hockey, et al. 2005). Diet This species is omnivorous, its diet consisting of agricultural grain; the seeds, fruits, roots, rhizomes and stems of aquatic plants, grasses (e.g. Panicum schinzii) and sedges (del Hoyo, et al. 1992, Hockey, et al. 2005, Kear 2005b); also aquatic molluscs, insects (mainly beetles) (Brown, et al. 1982), crustaceans, worms, tadpoles and even fish (Johnsgard 1978, del Hoyo, et al. 1992, Hockey, et al. 2005) (although these latter items are unusual) (Johnsgard 1978). In South Africa the species breeding diet consists largely of terrestrial seeds (e.g. of Panicum schinzii) with very few invertebrates (Petrie 1996, Kear 2005b). Breeding site The nest is a depression in a mound of grass on the ground amongst dense vegetation, usually near the waters edge (del Hoyo, et al. 1992).
There are potential threats from the leeches Theromyzon cooperi and Placobdella garoui which can lead to mortality in infested birds (Oosthuizen and Fourie 1985, Fourie, et al. 1986). The species is also threatened by habitat alteration in Madagascar (Scott and Rose 1996). Utilisation Although this species is extensively hunted and regarded as a favourite sporting target (Johnsgard 1978, del Hoyo, et al. 1992), there is no evidence that such activities pose a current threat to the species.
Text account compilers
Malpas, L., Butchart, S., Ekstrom, J.
BirdLife International (2020) Species factsheet: Anas erythrorhyncha. Downloaded from http://www.birdlife.org on 09/08/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 09/08/2020.