Northern Harrier (Circus cyaneus)

Photo by Jack BartholmaiNorthern Harrier by Jack BartholmaiNorthern Harrier distribution map


Population Information

Federal BBS information can be obtained at by clicking on Trend Estimates and selecting the species in question. All estimates are for 1966-2005.

Life History

Habitat Selection

Northern Harriers occur in undisturbed upland and wetland areas such as hayfields, pasture, medium to tall idle grasslands, old field, mesic to wet-mesic prairie, oak savanna, sedge meadow, and barrens. They favor larger grassland patches, typically >40 hectares (Sample and Mossman 1997, Johnson and Igl 2001). Northern Harriers are ground nesters and are known to nest near tall or dense patches of vegetation. In one Wisconsin study, dominant plant species near nests included willow (Salix sp.), grasses (Graminae), meadowsweet (Spirea alba), goldenrod (Solidago sp.), sedge (Carex and Scirpus spp.), and stinging nettle (Urtica dioica) (Hamerstrom and Kopeny 1981). Prey availability is also associated with habitat quality for this species. High prey abundance is positively correlated to productivity (Hamerstrom 1979).

Habitat Availability

Barrens, sedge meadow, idle grassland, and oak savanna habitats are currently rare in Wisconsin and vulnerable to conversion, development, and forest succession. Pastures and old fields are more common, but still vulnerable to heavy grazing or row crop conversion. The extensive grass meadows and marshes that this species favors are numerous only in the southern, eastern, and central portions of the state (Robbins 1991).

Population Concerns

Breeding Birds Survey data suggest significant population declines range-wide for this species. In Wisconsin, populations appear more stable (Sauer et al. 2005) and it remains a common migrant and resident throughout much of the state (Robbins 1991). During the six-year period (1995-2000) of the Wisconsin Breeding Bird Atlas, observers documented Northern Harriers breeding in 57 counties (Everard 2006).  

In North America, the Northern Harrier experienced population declines in the twentieth century due mostly to loss of habitat through extensive wetland draining, monotypic farming, and the reforestation of farmlands. Factors affecting local winter-population densities include prey availability, snow cover, temperature, and competition with other raptors (MacWhirter and Bildstein 1996).

Recommended Management

Northern Harriers in Wisconsin will benefit from continued large-scale grassland restoration and management within appropriate ecological landscapes (Sample and Mossman 1997, Knutson et al. 2001).  Areas managed for Greater Prairie-Chickens, another area-sensitive species, have provided breeding habitat for large numbers of harriers (Knutson et al. 2001). Wetland protection efforts for waterfowl and upland game bird management also will benefit Northern Harriers. Some of the conservation practices permitted by the Conservation Reserve Program (CRP) such as establishment of warm-season grasses and legumes and re-establishment of tilled wetlands can be beneficial to Northern Harriers. CRP participants should be encouraged to maintain CRP-approved vegetation after contracts expire (Hands et al. 1989).

Northern Harriers prefer idle habitats for nesting (Toland 1986, Herkert 1996), thus maintaining a mosaic of treated and untreated grasslands and wetlands is important (Johnson et al. 1998). No more than one-third of large areas (>40 hectares) should be burned in a given year (Sample and Mossman 1997). Avoid management activities during the breeding season, approximately April – July (MacWhirter and Bildstein 1996). Conservation and management strategies for this species should be focused in the following Wisconsin ecological landscapes: Central Sand Hills, Central Sand Plains, North Central Forest, Northern Lake Michigan Coastal, Northwest Lowlands, Northwest Sands, Southeast Glacial Plains, Southwest Savanna, Western Coulee and Ridges, and Western Prairie (WDNR 2005). Within these landscapes, the best public lands to manage for area sensitive species, such as the Northern Harrier, are White River Marsh Complex, Buena Vista/Leola Grasslands Landscape, and the Crex Meadows/Fish Lake Complex (Sample and Mossman 1997).

Research Needs

Much remains to be learned about the Northern Harrier outside the breeding season. Communal roost monitoring would provide considerable information regarding the distribution of sexes and the stability of wintering populations (MacWhirter and Bildstein 1996). Research is needed to determine the minimum size of habitat blocks needed to satisfy the requirements of harriers during the breeding, migratory, and wintering periods (Hands et al. 1989).

Information Sources


Contact Information

Kreitinger, K., Y. Steele and A. Paulios, editors. 2013.
The Wisconsin All-bird Conservation Plan, Version 2.0. Wisconsin Bird Conservation Initiative.
Wisconsin Department of Natural Resources. Madison, WI.

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