Justification 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.

Family/Sub-family Ardeidae

Species name author (Linnaeus, 1758)

Taxonomic source(s) AERC TAC (2003), AOU checklist (1998 + supplements), Christidis and Boles (1994), Christidis and Boles (2008), Cramp and Simmons (1977-1994), Dowsett and Forbes-Watson (1993), SACC (2005 + updates), Sibley and Monroe (1990, 1993), Stotz et al. (1996)

Population estimate

Population trend

Range estimate (breeding/resident)

Country endemic?

510,000 - 3,600,000

unset

52,400,000 km²

No

Important Bird Areas Click here to view map showing IBAs where species is recorded and triggers any of the IBA criteria.

Ecology: Behaviour Northern populations of this species are migratory, with those breeding in the western Palearctic travelling on a broad front across the Sahara¹ and those breeding in North American travelling on a narrow front along the Atlantic and Pacific coasts². Post-breeding southward movements occur from September to October and return northward movements occur from March to May². Tropical populations are not migratory but may undergo seasonal post-breeding dispersive movements¹. In temperate regions breeding occurs in the local spring, with tropical and subtropical nesting generally coinciding with the rains². The species usually nests in small numbers⁷ in single- or mixed-species colonies¹, although sometimes groups may reach several thousand pairs¹. When nesting within mixed-species colonies the species tends to form monospecific clusters². The species's aggregatory behaviour outside of the breeding season varies much throughout its range, some populations (e.g. in America) remaining highly gregarious throughout the year⁷ and gathering in flocks of hundreds or even thousands to roost¹, others (e.g. Palearctic breeders) being largely solitary except when roosting or on migration⁷ (roosting flocks of 2-6 to 200 are known in Africa⁵ and small flocks occur on migration)¹. The species is largely crepuscular and nocturnal, but may feed diurnally especially during the breeding season¹. Habitat The species inhabits fresh, brackish or saline waters with aquatic vegetation and bamboo or trees (e.g. pine, oak or mangroves) for roosting and nesting in¹, showing a preference for islands or predator-free areas for nesting sites². It occupies the forested margins of shallow rivers, streams, lagoons, pools, ponds, lakes, marshes and mangroves and may feed on pastures, reservoirs, canals, aquaculture ponds¹ and rice-fields (up to 96 % of a colony's food resources may be taken from nearby rice-fields)². On migration the species may also frequent dry grasslands or marine coasts¹, kelp beds² and estuaries⁶. It breeds up to 4,800 m (Chile)² but is more common at elevations of up to c.2,000 m⁷. Diet It is an opportunistic feeder taking fish, frogs, tadpoles, turtles, snakes, lizards, adult and larval insects¹ (e.g. beetles, bugs, grasshoppers, crickets, flies and dragonflies)², spiders, crustaceans, molluscs, leeches, small rodents, bats and the eggs and chicks of other bird species¹. Breeding site The nest is platform constructed of sticks and vegetation^{1, 2} placed 2-50 m above water or on dry ground near water⁷ in trees, bushes, reedbeds, on cliff ledges¹ (overhanging rivers)⁶ and on the ground¹ in protected sites². The species nests close together in single- and mixed-species colonies¹ with as many as 20-30 pairs in the same tree². Colony sites may be reused in consecutive years or flocks may move to new sites (usually such movements are a result of nesting trees being destroyed due to the colony's nesting activities)². Colony sites are dispersed throughout the landscape in relation to distance from feeding areas². Management information A study carried out in north-west Italy suggests that existing nesting sites should be protected and that breeding habitats should be actively managed in order to maintain suitable habitat characteristics¹³. The creation of a network of new nesting sites spaced at 4-10 km in relation to available foraging habitats in zones currently without suitable nesting sites is also recommended¹³.

Threats The species is threatened by wetland drainage and destruction^{1, 2} and by drought in wintering areas¹¹. It is highly susceptible to pesticides^{1, 2, 12} such as organophosphates, carbamates¹² and DDE (a breakdown product of DDT) which negatively affect hatching success². There are also cases of genetic damage to chicks as a result of petroleum contamination⁴. The species is susceptible to avian influenza⁸ and Newcastle disease so may be threatened by future outbreaks⁹. It is also persecuted (anti-predation killing) at aquaculture facilities due to its depredation on fish stocks², and has suffered declines due to the exploitation of chicks from nesting colonies in the past¹. Utilisation Chicks of the species are still taken for food in some areas (e.g. Madagascar)^{2, 3} and adults are hunted and traded at traditional medicine markets in Nigeria¹⁰.

References 1. del Hoyo et al. (1992). 2. Kushlan and Hancock (2005). 3. Hafner (200). 4. Custer (2000). 5. Brown et al. (1992). 6. Hockey et al. (2005). 7. Snow and Perrins (1998). 8. Melville and Shortridge (2006). 9. Kuiken et al. (2006). 10. Nikolaus (2001). 11. Hafner and Kushlan (2002). 12. Kwon et al. (2004). 13. Fasola and Alieri (1992).

Further web sources of information

Detailed species account from Birds in Europe: population estimates, trends and conservation status (BirdLife International 2004)

Text account compilers Stuart Butchart (BirdLife International), Jonathan Ekstrom (BirdLife International), Lucy Malpas (BirdLife International)

IUCN Red List evaluators Jeremy Bird (BirdLife International), Stuart Butchart (BirdLife International)

Recommended citation BirdLife International (2010) Species factsheet: Nycticorax nycticorax. Downloaded from http://www.birdlife.org on 30/7/2010

This information is based upon, and updates, the information published in BirdLife International (2000) Threatened birds of the world. Barcelona and Cambridge, UK: Lynx Edicions and BirdLife International, BirdLife International (2004) Threatened birds of the world 2004 CD-ROM and BirdLife International (2008) Threatened birds of the world 2008 CD-ROM. These sources provide the information for species accounts for the birds on the IUCN Red List.

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