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 may be moderately small to large, but it is not believed to 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 population trend is decreasing, although some populations may be stable and others have unknown trends (Wetlands International 2006).
Behaviour This species is partly migratory, undertaking both local and long-distance migrations within its southern African range (Scott and Rose 1996). South African populations migrate northwards during the dry season, and there is evidence that the species may congregate in the central parts of its range (Zambia, Tanzania) in the middle of the year in order to breed (Scott and Rose 1996). The exact timing of the breeding season varies according to locality and water levels (del Hoyo et al. 1992), but eggs are often laid towards the end of the wet season (Brown et al. 1982). During the breeding season Southern Pochard is usually encountered singly in pairs or small parties (Johnsgard 1978, Madge and Burn 1988, Kear 2005b). During the non-breeding season the species is relatively gregarious, with flocks of several hundred birds recorded at times (a concentration of 5,000 birds was once recorded) (Johnsgard 1978). Such large congregations usually only occur during the dry season however, when the reduction of water areas causes concentrations of birds to develop (Johnsgard 1978). In South Africa (Scott and Rose 1996) adult birds undergo a total wing-moult period between August and September when they are flightless for around 31 days (Brown et al. 1982). During this period adult birds seek refuge on open water when they are together in flocks, or remain close to beds of emergent aquatic vegetation such as reeds or sedges if they are solitary (Brown et al. 1982). The species is both diurnal and nocturnal, feeding during the day and sometimes during the night, and is most active in the early mornings and evenings (Brown et al. 1982). Habitat This species occurs on most still freshwater (and sometimes brackish water) (Madge and Burn 1988) habitats with abundant submerged vegetation, from sea level up to 2,400 m in East Africa (Brown et al. 1982, Madge and Burn 1988, Scott and Rose 1996, Kear 2005b). This includes shallow to deep, large to small, permanent or temporary pools or lakes, with or without emergent vegetation (Brown et al. 1982, Kear 2005b). It has recently been known to colonise reservoirs and rice paddy fields in South America (Kear 2005b) but is rarely seen on land (Brown et al. 1982). Generally it avoids rivers, turbid waters, very shallow temporary ponds and flooded areas (Johnsgard 1978). Diet The species is primarily vegetarian although it may take animal material (Johnsgard 1978). Its diet consists primarily of seeds but also roots and vegetative parts of aquatic or shoreline vegetation (including water-lilies, bladderwort, duckweeds, cattails, bulrushes, grasses, sedges and domestic rice) (Johnsgard 1978, Brown et al. 1982, del Hoyo et al. 1992, Kear 2005b), as well as aquatic beetles, snails, ants, hemipterans and crustaceans (Johnsgard 1978, Brown et al. 1982, Kear 2005b). Breeding site The nest is a basin-shaped construction of plant material that is usually well hidden in tall emergent vegetation such as papyrus, reeds or sedges, either above the water, along the bank or a little way from the water in tall grass (Kear 2005b). Nests have also occasionally been reported in exposed positions in sedge, on dam walls, in old antbear holes and in old nests of other water birds (Brown et al. 1982).
The South American population of this species has gone through a large decline, possibly due to habitat degradation (siltation caused by soil erosion degrades the rich macrophyte waterbodies favoured by the species) (Kear 2005b). In Africa this species is threatened through the transformation of wetlands into agricultural land (del Hoyo et al. 1992, Kear 2005b) and through entanglement in gill nets (Kear 2005b). The species is also susceptible to avian botulism, so may be threatened by future outbreaks of the disease (van Heerden 1974).
Text account compilers
Butchart, S., Ekstrom, J. & Malpas, L.
BirdLife International (2020) Species factsheet: Netta erythrophthalma. Downloaded from http://www.birdlife.org on 12/07/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 12/07/2020.