In the mildest regions, such as France and Great Britain, hen harriers may be present all year, but the higher ground is largely deserted in winter.

In 1758 the English naturalist George Edwards included an illustration and a description of the hen harrier in the first volume of his Gleanings of Natural History.

[3] When in 1766 the Swedish naturalist Carl Linnaeus updated his Systema Naturae for the twelfth edition, he placed the hen harrier with the falcons and eagles in the genus Falco.

Linnaeus included a brief description, coined the binomial name Falco cyaneus and cited Edwards' work.

[4] The hen harrier is now placed in the genus Circus that was introduced by the French naturalist Bernard Germain de Lacépède in 1799.

[13] The female gives a whistled piih-eh when receiving food from the male, and her alarm call is chit-it-it-it-it-et-it.

When incubating eggs, the female sits on the nest while the male hunts and brings food to her and the chicks.

[16] This is a typical harrier, which hunts on long wings held in a shallow V in its low flight during which the bird closely hugs the contours of the land below it.

Preferred avian prey include passerines of open country (i.e. sparrows, larks, pipits), small shorebirds and the young of waterfowl and galliforms.

Predators of eggs and nestlings include raccoons, skunks, badgers, foxes, crows and ravens, dogs and owls.

Short-eared owls are natural competitors of this species that favor the same prey and habitat, as well as having a similarly broad distribution.

Occasionally, both harriers and short-eared owls will harass each other until the victim drops its prey and it can be stolen, a practice known as kleptoparasitism.

[1] In Britain and Ireland, however, hen harrier populations are in a critical condition, due to habitat loss and illegal killing on grouse moors.

Unlike many raptors, hen harriers have historically been seen favorably by farmers because they eat predators of quail eggs and mice that damage crops.

[citation needed] The hen harrier is a bird of open habitats such as heather moorland and extensive agriculture.

However, much of its range, particularly in Ireland and parts of western Britain, has been (and continues to be) afforested, predominantly with non-native conifers such as Sitka spruce (Picea sitchensis) from North America.