The Northern Harrier (C. hudsonius) breeds in North America and northern Europe. The male's plumage is dark grey and the female is also dark and more rufous in colour. It has distinct male and female plumages. The sexes also differ in weight, with males weighing an average of 350 g and females an average of 530 g. The Northern Harrier is 45–55 cm long with a 97–118 cm wingspan.
It is a bird of the open country that builds its nest of the ground. Four to six whitish eggs are laid.
This species has a large range, with an estimated global extent 1–20 million km², and a population estimated at 1.3 million individuals.
There is evidence of a population decline, but the species is not believed to approach the thresholds for the population decline criterion.
Order: Falconiformes (or Accipitriformes, q.v.)
Species: C. cyaneus
*BirdLife International (2004). Circus cyaneus. 2006 IUCN Red List of Threatened Species. IUCN 2006. Retrieved on 11 May 2006. Database entry includes justification for why this species is of least concern
*del Hoyo, J., Elliott, A., & Sargatal, J., eds. (1994). Handbook of the Birds of the World Vol. 2. Lynx Edicions, Barcelona
*Mullarney, Killian; Svensson, Lars; Zetterstrom, Dan; Grant, Peter (1999). Collins Bird Guide. London: HarperCollins
*Ferguson-Lees, J., & Christie, D. A. (2001). Raptors of the World. Christopher Helm, London