In 1750 the English naturalist George Edwards included an illustration and a description of the northern harrier in the third volume of his A Natural History of Uncommon Birds.

Edwards based his hand-coloured etching on a bird collected near the Hudson Bay in Canada and brought to London by James Isham.

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

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

[3] The northern harrier is now placed in the genus Circus, introduced by the French naturalist Bernard Germain de Lacépède in 1799.

[11][12] The northern harrier is mostly silent,[13] although males and females will both give fast kek notes that will last 1-2 seconds.

When faced with predators or surrounded by smaller birds, they still emit kek notes but at a higher pitch.

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

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.

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