Associated Species: Species that may use habitat in a similar way and/or respond similarly to threats, management, and conservation activities include Virginia Rail, Sora, Common Snipe, Short-eared Owl, Marsh Wren, Red-winged Blackbird, and Yellow-headed Blackbird.

Distribution: Northern Harriers breed in North America and Eurasia. They breed throughout North America except for the South and Southeast, with their highest densities occurring in the northern prairie regions (Price et al. 1995). They reside throughout Colorado, with highest densities on the eastern plains, mountain parks, and western valleys.

Habitat Requirements: Northern Harriers breed in a wide array of habitats, but they typically prefer large tracts (100 ha; 250 ac) of wetlands with dense vegetation. Actual breeding habitat preferences are fairly broad and specific habitats include wet meadows, grasslands, sagebrush, and mountain shrublands. This species has a large home range (Craighead and Craighead 1956), which makes the researcher's task of locating nests difficult.

Ecology: Although breeding dates vary considerably with altitude, in Colorado Northern Harriers generally initiate breeding in late April. Females construct the nest on the ground in abundant cover. They incubate during May; incubation begins before laying is complete and lasts 24-30 days. Hatching takes place in June, and young spend approximately five weeks in the nest, leaving by early August. Females do the incubation and brooding, and males provide food for the females during this period and for the young. These hawks feed on small mammals, birds, reptiles and amphibians. They hunt by flying low over wetlands, grasslands, shrublands, and croplands. Their keen sense of hearing and sight make their low altitude hunting strategy successful.

Management Issues and Conservation Recommendations: The population of Northern Harriers has declined due to wetlands habitat losses. Large feeding areas are needed. Identify and protect larger wetlands used by this species. Erect buffers to incompatible land uses such as urban development..

In wetlands where water levels are regulated, nests become flooded by sudden rises in water levels. Do not allow water levels to rise more than 6 in (15 cm) during nesting season.

Large numbers of livestock permitted to graze in wetlands during the breeding season may accidentally trample nests or young. Stock wet meadow and wetland pastures at low level.

Habitat management schemes for waterfowl and upland game birds generally benefit harriers. Managers should continue to consider the potential benefits and impacts of such management to Northern Harriers.

Loss of prey species, either through direct control or through habitat loss, reduces populations. Maintain populations of voles at levels compatible with economic uses of the land.

Some nests are destroyed by agricultural equipment. Postpone haying until after the end of nesting, or avoid the area immediately around harrier nests.

Status and Reasons for Concern: This species has a moderately high conservation need throughout its range, along with high representation in the physiographic area and a declining population trend. The BBS data for 1966-1996 are too sparse for meaningful analysis of trends. Northern Harriers were present on an average of 6.99% (SE = 2.29) of BBS routes run in Physiographic Area 87 in Colorado, 1988 -1997, at an average abundance of 0.09 (SE = 0.03) individuals per route. The mean number of routes run each year was 11.4 (SE = 1.55). This species is monitored by MCB with point transects.

Biological Objective: Increase the species' distribution and abundance, based upon results of the BBS and MCB monitoring programs.

Selected References: Andrews and Righter 1992, Kingery 1998, MacWhirter and Bildstein 1996.