Northern Harrier

Formerly called Marsh Hawk, and for good reason. Northern Harrier is most commonly seen flying low over fields, meadows, marshes, and other wetlands looking for prey--particularly rodents, but also reptiles, amphibians and even the occasional small bird. Usually perches on the ground or low posts. Not numerous, but present year-round in Sonoma County. Numbers highest in the winter months as birds move in from other areas starting around late September. Numbers decline somewhat again from around April. Juveniles tend to outnumber adults in the winter. Known to nest in the county. According to the Breeding Bird Atlas, confirmed nesting sites include Bodega Head, the Petaluma River area, and near Tubbs Island, in the south of the county. Northern Harrier is a fairly common sight in appropriate habitat at Bodega Bay and elsewhere along the coast. Inland, often seen at Shollenberger Park, Ellis Creek Water Treatment Facility, and Tolay Lake Regional Park.

Northern Harrier may be the easiest of our more common diurnal raptors to identify. Even at long distances its habit of flying low over the ground in search of food--sometimes brushing the tops of tall grasses as it hunts--is distinctive. Wings often held in a distinct V while gliding. Buoyant, unstable-looking flight is typical. The patch of white feathers at the base of the tail is visible at long distances. Proportionately long wings and tail. At close range, note the owl-like facial disc (especially obvious in juveniles), which is believed to help the bird hunt by ear.

The two sexes are easily distinguished as adult birds. Females are larger and brownish above, pale buff and heavily streaked below, usually with primaries appearing slightly paler than the rest of the underwing when seen from below. Dark trailing edge to wing. A rare female may show a rufous wash below. Males are smaller and greyish--sometimes quite pale and ashy looking, sometimes tending towards a slaty color. Males are even paler below (almost white) but with contrasting dark wingtips (black outer primaries). Also darker at inner trailing edge of wing. Juveniles are cinnamon below, often (but not always) with some streaking on the upper breast and sides of the belly (although this is subtle and may not be visible in the field). The color fades to buff by the first spring. Inner half of the underwing is noticeably darker in juveniles and the facial disc is more obvious than in adults, as noted above. Generally speaking, juveniles of both sexes resemble females, both being brown-backed. As young birds lose their cinnamon coloring underneath, they look increasingly like adult females (that is, pale-breasted). At close range, however, note that juveniles will have a dark iris, adult females (and males) a pale iris.

Not likely to be confused with other birds, but the pale undertail coverts of Cooper’s Hawk (Accipiter cooperi) when seen from the side can momentarily look like the rump patch of a Harrier. Swainson’s Hawk (Buteo swainsoni) and many juvenile Red-tailed Hawks (Buteo jamaicensis) also have an area of pale feathers at the base of the tail, but it’s more saddle-shaped and much less starkly white. The Accipiters and Swainson’s Hawk may be distinguishable from Northern Harrier, however, by flight style (long flaps on lanky wings in Harrier) and habitat (unless on migration). In spring, during breeding season, male Harriers engage in display flight that is radically different from their usual pattern of flight. A Harrier appearing high in the sky at this time of year (or at any time) can confuse even veteran birders. Males may suggest White-tailed Kite (Elanus leucurus), but the two birds have very different flight habits.

*Note: There appears to be some disagreement about the Latin name of this bird. Some sources list Northern Harrier as Circus hudsonius, distinguishing the Northern Harrier of the Americas from Circus cyaneus, described as a Eurasian species, usually given the common name Hen Harrier. Some sources consider the North American bird a subspecies of Circus cyaneus--C. c. hudsonius. I’m not entirely sure what the current consensus is.

For current raptor migration information, visit the Golden Gate Raptor Observatory website

English synonyms: American Harrier, Marsh Hawk, North American Northern Harrier

Northern Harrier in other languages--German: Hudsonweihe; Spanish: Aguilucho Americano, Gavilán de Ciénaga, gavilán rastrero, Gavilán Sabanero; French: Busard, Busard d'Amérique, Busard des marais, Saint-Martin d'Amérique

Russian: Американский лунь; Japanese: アメリカチュウヒ(amerika chuuhi)

(Language information from Avibase, Birds of Europe (Mullarney et al, Princeton Field Guide Series), and Birds of Asia (Mark Brazil, Princeton Field Guide Series).