Bird of the Month: Northern Harrier
By Andy McCormick
Scientific Name: Circus cyaneus
Length 18" long
Weight 15 oz. (420 g)
AOU Band code NOHA
The Northern Harrier is the bird of many names. It is the Marsh Hawk which cruises low over marshes and fields. It is the Hen Harrier, as it is called in Europe and Asia, presumably because it made off with a hen every now and then. Most gloriously, it is the Sky Dancer. In spring the male Northern Harrier will circle high into the sky and just as it seems it will keep going up, it performs a somersault and dives in a dramatic swoop almost to the ground and then circles up again. The dancing is part of its courtship display. It must be effective, because male harriers are polygamous and will mate with several females, sometimes as many as three at one time. Pete Dunne says, “the sky dancing is a way of saying, ‘I’m the hottest, spunkiest, most capable (and most eager) harrier in the marsh.”
The responsibility of nurturing the offspring in multiple nests keeps the male very busy once the chicks hatch out. Harriers nest on the ground in a dense field or marsh. The nest is a shallow depression lined with grass. Generally 4-6 eggs are incubated by only the female for about a month. It takes the young another month to take flight so they are fed by parents during that time (Kaufman). The nest may be part of a loose colony, especially if the male has mated more than one female. Unlike many raptors, harriers will overlap their foraging area as they quarter fields in low flight (Dunne).
This flight pattern led to its name. Harrier refers to the bird’s “hunting behavior of flying close to the ground and harrying its prey” (Holloway). The Northern Harrier is the only North American representative from the genus Circus from the Greek kirkos, a circle or ring, for a kind of hawk that flies in circles. There are 14 species of harrier worldwide. The species name cyaneus, dark blue, references the bluish gray color on the back of the male Northern Harrier. The most obvious and helpful field marks for identification are the white upper tail coverts, often called a “rump patch,” which are visible in flight on both the male and female.
Northern Harriers share hunting areas with owls, often Short-eared Owls, with which they bear a striking resemblance when seen face on. Both species have a facial disk that focuses sound waves allowing them to track prey in the grass. They may eat songbirds and doves, voles and other rodents, small rabbits, insects, and snakes, lizards, frogs and toads (Kaufman).
North American Northern Harriers migrate through the central part of the continent, but significant numbers are seen along the Pacific Flyway in SE Alaska and British Columbia in both fall and spring. Some will overwinter in Washington. Most migrate to the southern United States and into Mexico. The population of Northern Harriers varies with availability of prey, chief of which are voles. In the 20th Century overall populations have declined primarily from loss of habitat due to draining of wetlands, monotypic farming and reforestation of farmlands. Since the 1990s continent-wide population has been fairly stable (Smith, et al).
You can see a male harrier soaring with a hint of sky dancing at Macauley Library.