Identification

Perching: Slender silhouette, long, banded tail, small head with owl-like facial disk. Males gray above and white below; females brown above with heavy brown streaking on breast. Juveniles chocolate brown underneath. Perches on the ground or on low fence post in wetland or grassland.

Flying: Long slender wings held in slight dihedral; tilts from side to side while gliding low near the ground. Prominent white rump patch (when viewed from above) on both sexes.

Nesting Habitat

Wetlands, grasslands, and shrublands, usually below 3000 m. Nest is a platform of grass, reeds, and cattails placed on the ground and concealed by thick vegetation. One male may nest with two or more females. When not nesting, harriers roost communally on the ground. Avoid walking through areas of dense grass or cattails.

Nesting Dates

Courtship: late April to late June

Incubation: early May to early July

Dependent nestlings: early June to mid-July

Clutch sizes range from 3-7 eggs. Incubation period is 29-31 days. Individual young hatch over a period of 1-10 days. Young fledge 30-40 days after hatching.

Statewide Distribution and Population

Nests throughout eastern plains, western valleys, and mountain parks. Colorado Breeding Bird Atlas efforts indicate a scattered distribution. Populations appear to be declining in areas where habitat has been fragmented by farming and urban expansion.

State and Federal Status

Colorado State Wildlife Action Plan Tier 2 species.

Search and Nest Monitoring Protocol

Beginning mid-April, observe potential nesting habitat for 2-3 hours every two weeks (early morning or early evening optimal) from one or more fixed observation points. Note behavior of males and females. Both engage in prominent courtship flights, and males perform "food drops" over active nests. Do not search for nests or approach within 400 m of suspected nest sites. If nest site is active, continue observations until mid-August or until all young have fledged.

Recommended Nest Buffer Area

No surface occupancy, foot traffic, or recreational activity within 400 m of suspected nest sites. Permanent trails should be located at least 400 m from recent nest or roost sites.

References

Bent, A. C. 1937. Life histories of North American birds of prey, part 1. U.S. National Museum Bulletin 167, Washington, D.C.

Craighead, J. J., and F. C. Craighead. 1956. Hawks, owls, and wildlife. Stackpole Books, Harrisburg, PA.

Johnsgard, P. A. 1990. Hawks, eagles, and falcons of North America. Smithsonian Institution press, Washington, D.C.

Kingery, H. E., ed. 1998. Colorado breeding bird atlas. Colorado Bird Atlas Partnership, Denver.

Rice, W. R. 1982. Acoustical location of prey by the Marsh Hawk: adaptation to concealed prey. Auk 99: 403-413.