Northern harrier

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Circus cyaneus

Type: bird

Status:

Species Guide

Northern harrier

Circus cyaneus

Species Type: bird

Conservation Status:

Identification

Northern harriers are often seen flying low over the open coastal marshes of New Jersey. They are a medium to large-sized hawk. They have a white "rump patch" that located above the tail. They often fly very low and the position of their wings look like a shallow "V." It has owl-like facial disk that aids it in detecting prey in tall grass or low-light conditions. It concentrates sound towards the ears. Adult northern harriers are sexually dimorphic, or the female and male look different, in both plumage and size. The males are smaller and have a slate gray color above and white below. They have contrasting black wingtips and a black back edge on the wing. The male’s white breast has varying amounts of light rufous (rusty) spotting. The female is larger and is brown above and buff colored below. They have brown vertical streaking on the chest and belly. The underwing of the female is dark and the black wingtips are masked. On all harriers, the white “rump patch” is a key in-flight field mark. Adult harriers have lemon yellow eyes. The legs are long and yellow. The cere (the fleshy area behind the base of the bill) is yellow. The bill is black.

Juvenile northern harriers are extremely similar in appearance to adult females.
Juveniles are slightly darker than adult females. They have a cinnamon wash to the underside that is faintly streaked. Juvenile males are born with grayish eyes that turn to a lemon-yellow by their first winter. Juvenile females have dark brown eyes that take at least two years to appear yellow.

Northern harriers employ several different calls. A chirp-like call between male and female is given during food exchange or on the ground during mating. This call is also exchanged between females and nestlings. The alarm call of harriers consists of a series of kaks when a predator or intruder disturbs the nesting area. The male often calls with a high-pitched, gull-like whine during courtship and territorial display flights. A Northern harrier hunting low over a marsh is one of the most distinctive raptors in flight.

Distribution & Habitat

Distribution and Habitat

The Northern harrier ranges throughout most of North America. It breeds from Canada and Alaska south to California and Texas in the West and through the Mid-Atlantic States south to Virginia in the East. They winter throughout the contiguous United States south to Mexico, Central America, the Caribbean Islands, and sometimes northern South America.

Formerly known as the “marsh hawk,” the northern harrier inhabits open areas such as tidal marshes, emergent wetlands, fallow fields, grasslands, meadows, airports, and agricultural areas. Many nests in the state occur along the Delaware Bay shore in brackish or saline marshes. Within these areas, harriers nest in the high marsh areas that are usually drier than low marsh areas. High marsh is dominated by salt hay (Spartina patens), marsh elder (Iva frutescens) or reed grass (Phragmites communis). Harriers may also nest in freshwater tidal marshes. Inland nesting sites may be located in managed, fallow, or low-intensity agricultural fields that contain tall grasses and herbaceous vegetation.

Northern harriers forage over marshes, fields, bushes, and edges that contain low vegetation, often only 3 to 6 ft. high. Phragmites may be used for nesting but it offers poor foraging habitat for harriers. It forms very dense and almost impenetrable stands of the vegetation.

Male and female harriers are different in size and they exhibit sexual variation in diet and foraging habitat. During the nesting season, females typically hunt within the marsh. Males forage in the marsh and often seek prey along upland edges and fields. Males can fly long distances while foraging for prey. They have larger home ranges than females. Individuals occupy larger territories during the winter when food is scarce.

Northern harriers occupy similar habitats throughout the year. Communal winter roosts of harriers are located on the ground within drier portions of marshes or in grasslands. Roost sites can be readily recognized. They are usually littered with pellets, feathers, and excrement.

Diet

Harriers are opportunistic. Generally they eat whatever is most abundant or available during the differing seasons. They are known to eat small mammals, birds, reptiles, amphibians, and insects. When prey numbers are down during unusually wet or cold weather in the breeding season the reproductive success of harriers is reduced.

In the summer months harriers mainly feed on the plentiful numbers of young songbirds, mammals, and reptiles and amphibians. In the winter their diet shifts to mainly small mammals, some birds, and carrion. Mammal prey includes voles, mice, shrews, rats, and rabbits.