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 population is thought to be stable (Wetlands International 2018).
Behaviour This species is an intra-African migrant, making nomadic or partially migratory movements of several hundred kilometres to breed during the rains (Brown et al. 1982, del Hoyo et al. 1992). Populations north of the equator migrate northwards and those south of the equator migrate southwards (Brown et al. 1982, del Hoyo et al. 1992), both groups returning towards the equator at the end of the breeding season (Brown et al. 1982). Some populations (e.g. in southern Africa) may also be sedentary (Hockey et al. 2005). The species starts to breed during or shortly after the rains, although in flooded areas it also breeds during the dry season, usually nesting in large mixed-species colonies of 50-2,000 pairs (del Hoyo et al. 1992). It is a very gregarious species, often flying more than 30 km away from the colony to feed (Brown et al. 1982, Hockey et al. 2005). The species also roosts nightly in large numbers at breeding sites, on islets in rivers or flood-lands, on trees near dams, or in villages (Brown et al. 1982). Habitat The species mainly inhabits the margins of inland freshwater wetlands, sewage works (del Hoyo et al. 1992), saltpans (Martin and Randall 1987), farm dams (Hockey et al. 2005), rivers in open forest (Brown et al. 1982), grasslands, and cultivated fields, as well as coastal lagoons, intertidal areas, offshore islands (del Hoyo et al. 1992) and mangroves (Langrand 1990) (especially in the dry season) (Hancock et al. 1992). It may also occur in more human environments such as farmyards, abattoirs and refuse dumps on the outskirts of towns (del Hoyo et al. 1992). Diet Its diet consists largely of insects including grasshoppers, locusts, crickets, and aquatic beetles, although it will also take crustaceans, worms, molluscs, fish, frogs, lizards, small mammals, the eggs of Great White Pelican Pelecanus onocrotalus and crocodiles, nestling Cape Cormorants Phalacrocorax capensis, carrion, offal and seeds (Brown et al. 1982, del Hoyo et al. 1992, Hancock et al. 1992). Breeding site The nest is a large platform of sticks and branches built in trees or bushes, or placed on the ground on rocky islands (Brown et al. 1982, del Hoyo et al. 1992).
The population on Aldabra Island has declined due to hunting and disturbance by temporary workers (del Hoyo et al. 1992). The species is also susceptible to avian botulism, so may be threatened by future outbreaks of the disease (van Heerden 1974).
Utilisation The eggs and young of this species are collected by local people in Madagascar (Langrand 1990, Hancock et al. 1992).
Text account compilers
Ekstrom, J., Malpas, L., Butchart, S.
BirdLife International (2019) Species factsheet: Threskiornis aethiopicus. Downloaded from http://www.birdlife.org on 26/03/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 26/03/2019.