New York Status: Threatened
Federal Status: Not Listed
The Northern harrier, formerly known as the marsh hawk, hunts primarily on the wing and may cover up to 100 miles per day. Its prey, consisting of mostly rodents and small birds, is detected using extremely keen hearing. This 16-24 inch, slender-bodied hawk has a long tail and wings, long yellow legs, distinct facial disks and a conspicuous white rump patch. In flight, the wings are held in a shallow "V." The adult male is pale gray on the head, back and wings. The gray tail is banded with six to eight gray-brown bars. There is cinnamon-brown spotting on the legs and flanks, and the wing linings and undertail are white. The eyes of an adult male are yellow.
Female plumage is browner overall with dark streaks on the breast. The female is born with brown eyes which turn yellow at about three years of age. Juveniles resemble adult females, but have gray eyes. When startled, this species makes a rapid, nasal chattering "ke-ke-ke-ke-ke".
This raptor is considered one of the most agile and acrobatic in North America. During the breeding season, the male performs an elaborate courtship flight consisting of a series of U-shaped maneuvers. The nest is a flimsy structure built of sticks and grass on the ground. It can be found in dense vegetation or situated in a slightly elevated position. The clutch averages five eggs. Incubation lasts 30-32 days and begins before the last egg is laid, so the young vary in size. The young fledge in 30-41 days, then remain near the nest, dependent on their parents for three to four weeks. Clutches are larger and reproductive success is higher during years when vole populations are high.
Distribution and Habitat
Northern harriers breed in North America from northern Alaska and Canada south to central and southern California, Mexico and portions of the southern U. S., excluding the southeast region. Wintering occurs from southern Canada to northern South America. Communal flocks roost on the ground during winter and migratory periods in agricultural fields, abandoned fields and salt marshes. Breeding occurs in both freshwater and brackish marshes, tundra, fallow grasslands, meadows, and cultivated fields.
Historically, populations of harriers were considered abundant and widespread. However, significant declines began in the 1950s and were attributed to factors such as loss of breeding habitat and effects of pesticides. Reforestation, filling in of wetlands, changes in land use, changes in agricultural practices and urban and industrial development all contributed to habitat losses.
The number of blocks in which this species was detected changed little from the first to second New York State Breeding Bird Atlases (a decrease of 1%) but some shifts in the species range appear to have occurred in the state. Although New York State breeding populations appear relatively stable, Breeding Bird Survey trend data shows a survey-wide decline for this species at 1.7% per year.
Management and Research Needs
Protection of suitable habitat is the most vital need of Northern harriers. They require vast expanses of relatively intact open habitat. Population size and reproductive success of this species are largely dependent upon prey populations. It has been well documented that harrier populations and populations of their prey follow similar patterns of fluctuation. It is important that any management allow for healthy prey populations and provide habitats that are suitable for them as well.
Research and monitoring by the DEC is currently underway for this and other grassland raptor species with the goal of creating a greater understanding of the conservation needs of these declining birds. Recent efforts have been made to more closely monitor and identify wintering raptor concentration areas throughout New York State with the Northern harrier included as a primary target species. This research has led to a better understanding of the importance of these concentration areas to the species, their response to changes in habitat and environmental conditions, and has led to the conclusive documentation of winter site fidelity for at least one location in New York State.