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LC
Northern Harrier Circus cyaneus

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 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.

Taxonomic source(s)
AERC TAC. 2003. AERC TAC Checklist of bird taxa occurring in Western Palearctic region, 15th Draft. Available at: http://www.aerc.eu/DOCS/Bird_taxa_of _the_WP15.xls.
AOU. 1998. Check-list of North American birds. American Ornithologists' Union, Washington, D.C.
Cramp, S.; Perrins, C. M. 1977-1994. Handbook of the birds of Europe, the Middle East and Africa. The birds of the western Palearctic. Oxford University Press, Oxford.
Dowsett, R. J.; Forbes-Watson, A. D. 1993. Checklist of birds of the Afrotropical and Malagasy regions. Tauraco Press, Li
SACC. 2006. A classification of the bird species of South America. Available at: http://www.museum.lsu.edu/~Remsen/SACCBaseline.html.
Sibley, C. G.; Monroe, B. L. 1990. Distribution and taxonomy of birds of the world. Yale University Press, New Haven, USA.
Stotz, D. F.; Fitzpatrick, J. W.; Parker, T. A.; Moskovits, D. K. 1996. Neotropical birds: ecology and conservation. University of Chicago Press, Chicago.

Taxonomic note

Circus cyaneus and C. hudsonius (del Hoyo et al. 2013) were previously lumped as C. cyaneus following Sibley and Monroe (1990, 1993).

Population justification
The global population is estimated to number > c.1,300,000 individuals (Rich et al. 2004), while national population estimates include: c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in China; < c.50 individuals on migration and < c.50 wintering individuals in Taiwan and c.10,000-100,000 breeding pairs and c.1,000-10,000 individuals on migration in Russia (Brazil 2009).

Trend justification
This species has undergone a small or statistically insignificant decrease over the last 40 years in North America (data from Breeding Bird Survey and/or Christmas Bird Count: Butcher and Niven 2007).

Ecology
Behaviour In the northern part of its range, it is completely migratory, wintering in Europe (Scotland and further south), extreme North Africa, southern Asia, and from southern Canada south to Colombia in the New World. It leaves breeding grounds between August and November, returning between March and May (del Hoyo et al. 1994). Birds are generally solitary and hunt alone but gather at concentrations of food and roosts, where they typically number tens of individuals, and may form loose flocks on migration (del Hoyo et al. 1994, Snow and Perrins 1998, Ferguson-Lees and Christie 2001). Migration is usually on a broad front, with birds willing to cross wide expanses of water and thus not concentrating at narrow crossing points as do many raptors (del Hoyo et al. 1994, Snow and Perrins 1998).  Habitat It is generally a bird of open country, where there is some limited cover from vegetation (del Hoyo et al. 1994). Diet It generally feeds on small vertebrates, mostly mammals and birds (del Hoyo et al. 1994, Ferguson-Lees and Christie 2001). Breeding site The nest is made in dense vegetation on the ground (del Hoyo et al. 1994). Management information The species requires open habitat but some shrub cover is necessary (del Hoyo et al. 1994).

Threats
A marked decline in the North American population in the 1950s-1960s is thought to have resulted from excessive use of harmful organochlorine pesticides. Currently, the major threat to the species is habitat loss, from agricultural intensification, wetland draining and afforestation in parts of its range (del Hoyo et al. 1994, Ferguson-Lees and Christie 2001). Persecution is an important threat locally, notably on game preserves in Scotland (del Hoyo et al. 1994). It is also highly vulnerable to the impacts of potential wind energy developments (Strix 2012).

References
Brazil, M. 2009. Birds of East Asia: eastern China, Taiwan, Korea, Japan, eastern Russia. Christopher Helm, London.

del Hoyo, J.; Elliott, A.; Sargatal, J. 1994. Handbook of the Birds of the World, vol. 2: New World Vultures to Guineafowl. Lynx Edicions, Barcelona, Spain.

Ferguson-Lees, J.; Christie, D. A. 2001. Raptors of the world. Christopher Helm, London.

Rich, T.D.; Beardmore, C.J.; Berlanga, H.; Blancher, P.J.; Bradstreet, M.S.W.; Butcher, G.S.; Demarest, D.W.; Dunn, E.H.; Hunter, W.C.; Inigo-Elias, E.E.; Martell, A.M.; Panjabi, A.O.; Pashley, D.N.; Rosenberg, K.V.; Rustay, C.M.; Wendt, J.S.; Will, T.C.

Snow, D. W.; Perrins, C. M. 1998. The Birds of the Western Palearctic vol. 1: Non-Passerines. Oxford University Press, Oxford.

Strix. 2012. Developing and testing the methodology for assessing and mapping the sensitivity of migratory birds to wind energy development. BirdLife International, Cambridge.

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

Text account compilers
Butchart, S., Ekstrom, J., Khwaja, N.

Recommended citation
BirdLife International (2014) Species factsheet: Circus cyaneus. Downloaded from http://www.birdlife.org on 23/07/2014. Recommended citation for factsheets for more than one species: BirdLife International (2014) IUCN Red List for birds. Downloaded from http://www.birdlife.org on 23/07/2014.

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.

To provide new information to update this factsheet or to correct any errors, please email BirdLife

To contribute to discussions on the evaluation of the IUCN Red List status of Globally Threatened Birds, please visit BirdLife's Globally Threatened Bird Forums.

Additional resources for this species

ARKive species - Northern harrier (Circus cyaneus) 0

Key facts
Current IUCN Red List category Least Concern
Family Accipitridae (Osprey, kites, hawks and eagles)
Species name author (Linnaeus, 1766)
Population size mature individuals
Population trend Decreasing
Distribution size (breeding/resident) 29,900,000 km2
Country endemic? No
Links to further information
- Additional Information on this species