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 global population is estimated to number c.270,000-570,000 individuals (Wetlands International 2015). This roughly equates to 180,000-380,000 mature individuals. The European population is estimated at 31,600-46,000 pairs, which equates to 63,100-92,100 mature individuals (BirdLife International 2015).
The overall population trend is decreasing, although some populations may be stable and others have unknown trends (Wetlands International 2015). The European population trend is estimated to be decreasing (BirdLife International 2015).
Behaviour Populations breeding in the western Palearctic are migratory and travel on a broad front between breeding and wintering grounds (del Hoyo et al. 1992, Kushlan and Hancock 2005). African and tropical-Asian populations are largely sedentary however, occasionally making local dispersive movements (del Hoyo et al. 1992). The species breeds from April to June in the western Palearctic, during the rains in Africa, and from June to October in the north of India or November to March in the south of India (del Hoyo et al. 1992). It is a colonial breeder and although nesting group sizes are usually small (e.g. 2-3 pairs per colony in Africa) and rarely exceed 50 pairs, colonies of up to 1,000 pairs have been recorded in some areas (Hancock and Kushlan 1984, del Hoyo et al. 1992, Turner 2000, Kushlan and Hancock 2005). It often also nests on the periphery of colonies of other heron species such as Grey Heron Ardea cinerea (Kushlan and Hancock 2005). In migratory populations, the autumn migration occurs from August to October, with the return passage in the spring beginning in March (Hancock and Kushlan 1984). On migration, the species commonly occurs in small groups (the maximum recorded migratory groups sizes being 300-400 individuals) and throughout the year it will roost communally by day and by night in groups of up to 100 individuals, although it generally feeds solitarily (Brown et al. 1982, Hancock and Kushlan 1984, del Hoyo et al. 1992). The species is mainly crepuscular, but may also feed diurnally (del Hoyo et al. 1992).
Habitat The species inhabits wetlands from sea level to 1,800 m (Madagascar), showing a preference for dense, flooded, freshwater reedbeds (Phragmites spp.) in temperate areas (occupying Typha, Scirpus and Papyrus swamps elsewhere) (del Hoyo et al. 1992, Kushlan and Hancock 2005). It also utilises lake shores, river margins, ditches, canals, brackish water lagoons, rice-fields, mangroves and coastal mudflats (del Hoyo et al. 1992, Kushlan and Hancock 2005).
Diet Its diet consists of fish 5-15 cm long (occasionally up to 55 cm), salamanders, frogs, insects (e.g. beetles, dragonflies, hemiptera and locusts), crustaceans, spiders and molluscs, as well as small birds and mammals, snakes and lizards (Hancock and Kushlan 1984, del Hoyo et al. 1992, Kushlan and Hancock 2005).
Breeding site The nest is a platform of reeds stems or sticks positioned over or beside water up to 3 m high in flooded reedbeds, 3-4 m high in thickets or mangroves or up to 25 m high in trees (del Hoyo et al. 1992, Kushlan and Hancock 2005). The species usually nests in loose single- or mixed-species colonies with Grey Heron Ardea cinerea, and although colony sizes are usually small, large groups of up to 1,000 pairs have been recorded (the colony size depends on the size of the area of marshland) (Hancock and Kushlan 1984, del Hoyo et al. 1992, Kushlan and Hancock 2005).
Management information Studies in southern France have shown that the overall conservation of this species in Europe is favoured by maintaining large uncut reedbeds with relatively high spring water levels (Barbraud et al. 2002).
The main threat to this species in Europe is the loss of reedbeds though direct elimination (to reduce sedimentation) (Kushlan and Hancock 2005), agricultural encroachment (Hockey et al. 2005), water management practices (Kushlan and Hancock 2005) (e.g. drainage) (Hockey et al. 2005) and reed cane harvesting (Kushlan and Hancock 2005).
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: Studies in southern France have shown that the overall conservation of this species in Europe is favoured by maintaining large uncut reedbeds with relatively high spring water levels (Barbraud et al. 2002). Freshwater habitats need to be sustainably managed and non-intrusion zones established around colonies.
Text account compilers
Malpas, L., Ekstrom, J., Ashpole, J, Everest, J., Butchart, S.
BirdLife International (2020) Species factsheet: Ardea purpurea. Downloaded from http://www.birdlife.org on 28/10/2020. Recommended citation for factsheets for more than one species: BirdLife International (2020) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 28/10/2020.