HARRIER, the name of birds of prey forming the genus Circus. Harriers affect open country, feeding on snakes, frogs and other small vertebrates. The long wings and legs and the frill surrounding the lower part of the head serve to distinguish them. The group is almost world-wide in distribution.
The commonest species is the hen-harrier (C. cyaneus), ranging over N. Europe and Asia and showing great sexual dimorphism. Montague's harrier (C. cineraceus), with a more southerly range, shows the same phenomenon, but is distinguished by its longer wings. The American marsh-hawk (C. liudsonius) is very similar to the hen-harrier, but the male has rufous markings below. Other species occur in Europe, Africa, Asia, S. America, Australia and New Zealand.
Harriers build large nests on or near the ground, in marshes or similar situations. When the male brings food for the female during incubation, she leaves the nest, he drops the prey and she catches it in mid-air. In Great Britain, three species are found (the first two mentioned above and C. aeruginosus, the marsh harrier), but all are now very rare. Harriers are extremely light (Montague, Ornithological Dictionary, 1802, gives the weight of the male as 13oz.) , but have a wing-spread of as much as 3 f t.