Taxonomy [top]

Kingdom Phylum Class Order Family
Animalia Chordata Aves Pelecaniformes Ardeidae

Scientific Name: Nycticorax nycticorax
Species Authority: (Linnaeus, 1758)
Regional Assessments:
Common Name(s):
English Black-crowned Night-heron, Black-crowned Night-Heron., Black-crowned Night-Heron, Black-crowned Night Heron, Night Heron
French Héron bihoreau
Taxonomic Source(s): del Hoyo, J., Collar, N.J., Christie, D.A., Elliott, A. and Fishpool, L.D.C. 2014. HBW and BirdLife International Illustrated Checklist of the Birds of the World. Lynx Edicions BirdLife International.

Assessment Information [top]

Red List Category & Criteria: Least Concern ver 3.1
Year Published: 2012
Date Assessed: 2012-05-01
Assessor(s): BirdLife International
Reviewer(s): Butchart, S. & Symes, A.
Facilitator/Compiler(s): Ekstrom, J., Butchart, S., Malpas, L.
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.
Previously published Red List assessments:
2009 Least Concern (LC)
2008 Least Concern (LC)
2004 Least Concern (LC)
2000 Lower Risk/least concern (LR/lc)
1994 Lower Risk/least concern (LR/lc)
1988 Lower Risk/least concern (LR/lc)

Geographic Range [top]

Countries occurrence:
Afghanistan; Albania; Algeria; Angola (Angola); Anguilla; Antigua and Barbuda; Argentina; Armenia (Armenia); Aruba; Austria; Azerbaijan; Bahamas; Bahrain; Bangladesh; Barbados; Belarus; Belgium; Belize; Benin; Bermuda; Bhutan; Bolivia, Plurinational States of; Bonaire, Sint Eustatius and Saba; Bosnia and Herzegovina; Botswana; Brazil; Brunei Darussalam; Bulgaria; Burkina Faso; Burundi; Cambodia; Cameroon; Canada; Cayman Islands; Central African Republic; Chad; Chile; China; Colombia; Comoros; Congo; Congo, The Democratic Republic of the; Costa Rica; Côte d'Ivoire; Croatia; Cuba; Curaçao; Cyprus; Czech Republic; Dominica; Dominican Republic; Ecuador; Egypt; El Salvador; Equatorial Guinea; Eritrea; Ethiopia; Falkland Islands (Malvinas); France; French Guiana; Gabon; Gambia; Georgia; Germany; Ghana; Greece; Grenada; Guadeloupe; Guam; Guatemala; Guinea; Guinea-Bissau; Guyana; Haiti; Honduras; Hong Kong; Hungary; India; Indonesia; Iran, Islamic Republic of; Iraq; Israel; Italy; Jamaica; Japan; Jordan; Kazakhstan; Kenya; Korea, Republic of; Kuwait; Lao People's Democratic Republic; Lebanon; Lesotho; Liberia; Macao; Macedonia, the former Yugoslav Republic of; Madagascar; Malawi; Malaysia; Mali; Malta; Martinique; Mauritania; Mayotte; Mexico; Micronesia, Federated States of ; Moldova; Montenegro; Montserrat; Morocco; Mozambique; Myanmar; Namibia; Nepal; Netherlands; Nicaragua; Niger; Nigeria; Northern Mariana Islands; Oman; Pakistan; Palau; Palestinian Territory, Occupied; Panama; Paraguay; Peru; Philippines; Poland; Portugal; Puerto Rico; Qatar; Romania; Russian Federation; Rwanda; Saint Kitts and Nevis; Saint Lucia; Saint Vincent and the Grenadines; Saudi Arabia; Senegal; Serbia (Serbia); Sierra Leone; Singapore; Slovakia; Slovenia; Somalia; South Africa; South Georgia and the South Sandwich Islands; South Sudan; Spain (Canary Is.); Sri Lanka; Sudan; Suriname; Swaziland; Switzerland; Syrian Arab Republic; Taiwan, Province of China; Tajikistan; Tanzania, United Republic of; Thailand; Timor-Leste; Togo; Trinidad and Tobago; Tunisia; Turkey; Turkmenistan; Turks and Caicos Islands; Uganda; Ukraine; United Arab Emirates; United States (Georgia, Hawaiian Is.); Uruguay; Uzbekistan; Venezuela, Bolivarian Republic of; Viet Nam; Virgin Islands, British; Virgin Islands, U.S.; Western Sahara; Yemen; Zambia; Zimbabwe
Australia; Cape Verde; Cocos (Keeling) Islands; Denmark; Djibouti; Faroe Islands; Finland; French Southern Territories; Gibraltar; Greenland; Iceland; Ireland; Korea, Democratic People's Republic of; Kyrgyzstan; Libya; Liechtenstein; Luxembourg; Maldives; Mongolia; Norway; Saint Helena, Ascension and Tristan da Cunha; Saint Pierre and Miquelon; Sao Tomé and Principe; Seychelles; Sweden; United Kingdom
Continuing decline in area of occupancy (AOO): Unknown
Extreme fluctuations in area of occupancy (AOO): No
Estimated extent of occurrence (EOO) - km2: 41200000
Continuing decline in extent of occurrence (EOO): Unknown
Extreme fluctuations in extent of occurrence (EOO): No
Continuing decline in number of locations: Unknown
Extreme fluctuations in the number of locations: No
Upper elevation limit (metres): 4800
Range Map: Click here to open the map viewer and explore range.

Population [top]

Population: The global population is estimated to number c.510,000-3,600,000 individuals (Wetlands International 2006), while national population estimates include: c.100,000-1 million breeding pairs, >c.10,000 individuals on migration and >c.10,000 wintering individuals in China; c.100,000-1 million breeding pairs in Taiwan; c.10,000-100,000 breeding pairs and c.50-1,000 wintering individuals in Korea and c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Japan (Brazil 2009).

Trend Justification:  The overall population trend is decreasing, although some populations may be stable, others have unknown trends (Wetlands International 2006). This species has undergone a large and statistically significant increase over the last 40 years in North America (294% increase over 40 years, equating to a 40.8% 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.
For further information about this species, see 22697211_nycticorax_nycticorax.pdf.
A PDF viewer such as Adobe Reader is required.
Current Population Trend: Decreasing
Additional data:
Continuing decline of mature individuals: Unknown
Extreme fluctuations: No Population severely fragmented: No
Continuing decline in subpopulations: Unknown
Extreme fluctuations in subpopulations: No All individuals in one subpopulation: No

Habitat and Ecology [top]

Habitat and Ecology: Behaviour Northern populations of this species are migratory, with those breeding in the western Palearctic travelling on a broad front across the Sahara (del Hoyo et al. 1992) and those breeding in North American travelling on a narrow front along the Atlantic and Pacific coasts (Kushlan and Hancock 2005). Post-breeding southward movements occur from September to October and return northward movements occur from March to May (Kushlan and Hancock 2005). Tropical populations are not migratory but may undergo seasonal post-breeding dispersive movements (del Hoyo et al. 1992). In temperate regions breeding occurs in the local spring, with tropical and subtropical nesting generally coinciding with the rains (Kushlan and Hancock 2005). The species usually nests in small numbers (Snow and Perrins 1998) in single- or mixed-species colonies (del Hoyo et al. 1992), although sometimes groups may reach several thousand pairs (del Hoyo et al. 1992). When nesting within mixed-species colonies the species tends to form monospecific clusters (Kushlan and Hancock 2005). 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 year (Snow and Perrins 1998) and gathering in flocks of hundreds or even thousands to roost (del Hoyo et al. 1992), others (e.g. Palearctic breeders) being largely solitary except when roosting or on migration (Snow and Perrins 1998) (roosting flocks of 2-6 to 200 are known in Africa (Brown et al. 1992) and small flocks occur on migration) (del Hoyo et al. 1992). The species is largely crepuscular and nocturnal, but may feed diurnally especially during the breeding season (del Hoyo et al. 1992). 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 in (del Hoyo et al. 1992), showing a preference for islands or predator-free areas for nesting sites (Kushlan and Hancock 2005). It occupies the forested margins of shallow rivers, streams, lagoons, pools, ponds, lakes, marshes and mangroves and may feed on pastures, reservoirs, canals, aquaculture ponds (del Hoyo et al. 1992) and rice-fields (up to 96 % of a colony's food resources may be taken from nearby rice-fields) (Kushlan and Hancock 2005). On migration the species may also frequent dry grasslands or marine coasts (del Hoyo et al. 1992), kelp beds (Kushlan and Hancock 2005) and estuaries (Hockey et al. 2005). It breeds up to 4,800 m (Chile) (Kushlan and Hancock 2005) but is more common at elevations of up to c.2,000 m (Snow and Perrins 1998). Diet It is an opportunistic feeder taking fish, frogs, tadpoles, turtles, snakes, lizards, adult and larval insects (del Hoyo et al. 1992) (e.g. beetles, bugs, grasshoppers, crickets, flies and dragonflies) (Kushlan and Hancock 2005), spiders, crustaceans, molluscs, leeches, small rodents, bats and the eggs and chicks of other bird species (del Hoyo et al. 1992). Breeding site The nest is platform constructed of sticks and vegetation (del Hoyo et al. 1992, Kushlan and Hancock 2005) placed 2-50 m above water or on dry ground near water (Snow and Perrins 1998) in trees, bushes, reedbeds, on cliff ledges (del Hoyo et al. 1992) (overhanging rivers) (Hockey et al. 2005) and on the ground (del Hoyo et al. 1992) in protected sites (Kushlan and Hancock 2005). The species nests close together in single- and mixed-species colonies (del Hoyo et al. 1992) with as many as 20-30 pairs in the same tree (Kushlan and Hancock 2005). 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) (Kushlan and Hancock 2005). Colony sites are dispersed throughout the landscape in relation to distance from feeding areas (Kushlan and Hancock 2005). 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 characteristics (Fasola and Alieri 1992). 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 recommended (Fasola and Alieri 1992).
Systems: Terrestrial; Freshwater; Marine
Continuing decline in area, extent and/or quality of habitat: Unknown
Generation Length (years): 8.8
Movement patterns: Full Migrant
Congregatory: Congregatory (and dispersive)

Threats [top]

Major Threat(s): The species is threatened by wetland drainage and destruction (del Hoyo et al. 1992, Kushlan and Hancock 2005) and by drought in wintering areas (Hafner and Kushlan 2002). It is highly susceptible to pesticides (del Hoyo et al. 1992, Kwon et al. 2004, Kushlan and Hancock 2005) such as organophosphates, carbamates (Kwon et al. 2004) and DDE (a breakdown product of DDT) which negatively affect hatching success (Kushlan and Hancock 2005). There are also cases of genetic damage to chicks as a result of petroleum contamination (Custer 2000). The species is susceptible to avian influenza (Melville and Shortridge 2006) and Newcastle disease so may be threatened by future outbreaks (Kuiken et al. 2006). It is also persecuted (anti-predation killing) at aquaculture facilities due to its depredation on fish stocks (Kushlan and Hancock 2005), and has suffered declines due to the exploitation of chicks from nesting colonies in the past (del Hoyo et al. 1992). Utilisation Chicks of the species are still taken for food in some areas (e.g. Madagascar) (Kushlan and Hancock 2005, Hafner 200) and adults are hunted and traded at traditional medicine markets in Nigeria (Nikolaus 2001).

Citation: BirdLife International. 2012. Nycticorax nycticorax. The IUCN Red List of Threatened Species 2012: e.T22697211A40264977. . Downloaded on 10 October 2015.
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