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 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.
The global population is estimated at 230,000-2,220,000 individuals (Wetlands International 2015). The European population is estimated at 28,300-37,700 pairs, which equates to 56,500-75,400 mature individuals (BirdLife International 2015). The population is therefore placed in the band 200,000-2,300,000 individuals.
The overall population trend is decreasing, although some populations have stable trends (Wetlands International 2015). This species has undergone a large and statistically significant increase over the last 40 years in North America (3,800% increase over 40 years, equating to a 150% increase per decade; data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007) Note, however, that these surveys cover less than 50% of the species's range in North America. In Europe the population size is estimated to be increasing (BirdLife International 2015).
Behaviour All populations of this species undergo post-breeding dispersal movements (del Hoyo et al. 1992) and are considerably nomadic (Snow and Perrins 1998). In addition northern breeding populations are fully migratory (del Hoyo et al. 1992) and may travel on a broad front (e.g. across the Sahara) (Brown et al. 1982). Northern and southern breeding populations breed during the local spring, whilst breeding elsewhere coincides with the rains (del Hoyo et al. 1992). The species nests in mixed-species colonies, either in small groups (e.g. 5-100 pairs in Africa) (Brown et al. 1982) or in large aggregations of thousands of pairs, and during the winter or dry seasons the species usually forages in small flocks (Hancock et al. 1992, del Hoyo et al. 1992) of up to 30 indivduals (Brown et al. 1982). It often roosts communally at night in large groups (sometimes thousands of individuals) with other species, occasionally in trees far from wetland feeding sites (Brown et al. 1982). Habitat The species feeds in very shallow water (Hancock et al. 1992) and nests in freshwater or brackish wetlands with tall dense stands of emergent vegetation (e.g. reeds or rushes) and low trees or bushes (Marchant and Higgins 1990, del Hoyo et al. 1992). It shows a preference for marshes at the edges of lakes and rivers (Hancock et al. 1992), as well as lagoons, flood-plains, wet meadows (Marchant and Higgins 1990, del Hoyo et al. 1992), swamps (del Hoyo et al. 1992), reservoirs (Hancock et al. 1992), sewage ponds, rice-fields and irrigated cultivation (Marchant and Higgins 1990, del Hoyo et al. 1992). It less often occurs in coastal locations such as estuaries, deltas, saltmarshes (Hancock et al. 1992) and coastal lagoons (del Hoyo et al. 1992). Roosting sites are often large trees that may be far from water (Brown et al. 1982, del Hoyo et al. 1992). Diet The diet of the species varies seasonally depending on what is available (Hancock et al. 1992). It takes adult and larval insects (e.g. aquatic beetles, dragonflies, grasshoppers, crickets, flies and caddisflies), worms, leeches, molluscs (e.g. snails and mussels), crustaceans (e.g. crabs and crayfish) and occasionally fish, frogs, tadpoles, lizards, small snakes and nestling birds (del Hoyo et al. 1992). Breeding site The nest is a platform of twigs and vegetation usually positioned less than 1 m above water (occasionally up to 7 m) in tall dense stands of emergent vegetation (e.g. reeds or rushes), low trees or bushes over water (del Hoyo et al. 1992).
The species is threatened by wetland habitat degradation and loss (del Hoyo et al. 1992, Snow and Perrins 1998) through drainage (Marchant and Higgins 1990, Hancock et al. 1992) for irrigation and hydroelectric power production (Balian et al. 2002), clearing, grazing, burning, increased salinity, groundwater extraction and invasion by exotic plants (Marchant and Higgins 1990). It is also threatened locally by hunting (del Hoyo et al. 1992, Snow and Perrins 1998), disturbance and pesticides (del Hoyo et al. 1992), and is susceptible to avian influenza so may be threatened by future outbreaks of the virus (Melville and Shortridge 2006).
Conservation Actions Underway
The species is listed on Annex I of the EU Birds Directive, Annex II of the Bern Convention and Annex II of the Convention on Migratory Species, under which it is covered by the African-Eurasian Waterbird Agreement (AEWA).
Conservation Actions Proposed
The following information refers to the species's European range only: Sustainably manage river valleys and wet grasslands; Abandonment of pastoral grassland, afforestation of farmland and drainage of wet meadows and inland wetlands in key breeding areas should be stopped.
Text account compilers
Ashpole, J, Butchart, S., Ekstrom, J., Malpas, L.
BirdLife International (2019) Species factsheet: Plegadis falcinellus. Downloaded from http://www.birdlife.org on 15/11/2019. Recommended citation for factsheets for more than one species: BirdLife International (2019) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 15/11/2019.