Northern Harrier

Northern Harrier (Circus cyaneus)

Gerald R. Urquhart

Status: Special Concern (MNFI)

Lenawee Co., MI. 2/26/2009. © Darlene Friedman (Click to view a comparison of Atlas I to II)

In

grasslands and marshes, ghostly male and brownish female Northern Harriers hunt low over the fields, gliding back and forth in search of small rodents and birds. They are familiar yet special birds in Michigan, with less frequent breeding than their familiarity suggests, and great vulnerability due to their habitat requirements. The Northern Harrier has a circumpolar distribution through two subspecies, with the North American subspecies being commonly called the Northern Harrier (formerly Marsh Hawk) and the Eurasian commonly referred to as the Hen Harrier (MacWhirter and Bildstein 1996). In North America, the breeding range of the Northern Harrier extends from Alaska and Newfoundland south to Baja California in the west, across the Great Plains, and to the Atlantic Seaboard. Harriers are highly migratory, with birds spreading from southern Canada to northern South America during winter months. Distribution In Michigan, the Northern Harrier is sparsely distributed throughout the state, with lower densities in the southern third of the LP. Surveys found breeding evidence in fewer townships during MBBA II (18.81%) than in

MBBA I (27.22%), a 30% decrease in the number of townships with breeding evidence. Although these figures do not represent actual population estimates, they do suggest that the previously uncommon Northern Harrier should be considered a rare breeder in Michigan. From MBBA I to MBBA II, breeding evidence declined in each of the areas that Yunger (1991) identified as “high breeding concentration.” The declines in each area are: 1) GladwinMidland county wetlands (-59%), 2) southcentral UP wetlands (-39%); 3) the eastern UP wetlands (-39%); and 4) the thumb region grasslands (-12%). Breeding Biology Northern Harriers migrate in March and April to their breeding areas in Michigan. From early April through May, the harriers perform a spectacular aerial display to attract mates. The male or male and female together flap their way up into the sky—as high as 300 meters—and then stoop toward the ground at high velocity, curving through a U-shaped flight bottoming out near the ground, and returning skyward (Bent 1939). Unlike most raptors, Northern Harrier males are occasionally polygynous, simultaneously breeding with two to five females (Simmons et al. 1987).

© 2011. Kalamazoo Nature Center

Northern Harrier (Circus cyaneus)

Gerald R. Urquhart

Status: Special Concern (MNFI) Harriers feed mostly on voles and other rodents, although grassland birds (Red-winged Blackbirds, Eastern Meadowlarks, and others) make up a small portion of their diet (MacWhirter and Bildstein 1986). Birds living in wet areas also consume frogs. Harriers nest on the ground in grassy fields or on elevated hummocks in marshes and bogs, locating their nests in the densest and tallest vegetation in the habitat. The nests are built of twigs and sticks with a cup of 20-25 cm wide and 5-10 cm deep, and outside diameter of 3963 cm. After nest construction, females begin laying eggs at two to three day intervals for a typical clutch of four to five eggs (Macwhirter and Bildstein 1996, Bent 1939). Egg laying in Michigan occurs mostly during May (late Aprilearly June; Craighead and Craighead 1969). Incubation lasts 30-32 days during which females remain on the nest for all but brief absences (MacWhirter and Bildstein 1996). Male harriers provide all food to females during incubation and most food to young in the first 10-14 days after hatching (Simmons et al. 1987). During this period, females brood the young and apportion food to nestlings, with older nestlings receiving more food. As nestlings grow, females begin to hunt and remain responsible for feeding the young. Young begin flying around 30-45 days, and remain in family groups for up to four weeks after fledging (MacWhirter and Bildstein 1996). Abundance and Population Trends The results of MBBA II surveys support the need for concern over decreasing populations, with an overall decrease of ~30% in townships with breeding evidence since MBBA I. A century ago, Barrows (1912) called the Northern Harrier “one of our commonest and best known birds,” but there have been significant changes in both habitat availability

and harrier population since. Because of its affinity for open grasslands and wetlands, it has been hit on multiple fronts by land use changes. Agricultural intensification—including reduced acreage in hayfields, shortened harvesting cycles and the increased use of pesticide—has reduced suitable habitat for Northern Harrier breeding. Wetlands have declined in Michigan since the 1830s (Dahl and Allord 1996). Between MBBA I and MBBA II, there were breeding evidence declines of 39%-59% in the three regions where harriers utilized extensive wetlands, with a lesser decline in the grassland region in the thumb. The declines suggest that changes in the wetland habitats may have impacted the populations in the centers of abundance. However, the Upper Peninsula regions also had further regrowth of forests logged in the early 1900s, and this may have fragmented grasslands and wetlands to the point of making them unsuitable. Gladwin and Midland Counties are home to large hayfields, and earlier first cuts of hay have negatively impacted many grassland birds (Bollinger et al. 1990, Giuliano and Daves 2002). In sum, multiple factors may be involved in the current declines in Northern Harriers in Michigan. Northern Harriers and the state-endangered Short-eared Owl are the two major grassland raptor species in Michigan. Both species breed in large, undisturbed wet meadows and grasslands with tall and often dense vegetation (Currier 2001). The minimum habitat size required for breeding is not well established, although territory sizes averaged 260 hectares (640 acres) in Washtenaw County (Craighead and Craighead 1969). In Illinois, Herkert et al. (1999) found harriers nesting in grasslands ranging from eight to 120 hectares, but suggested proximity to adjacent grassland areas was important for pairs nesting in small fragments. Based on the breeding records for Michigan, it appears that the scattered prairie remnants of SW Michigan do not provide


Northern Harrier (Circus cyaneus) Status: Special Concern (MNFI) enough nesting habitat for Northern Harriers, which may be because of their often small size (5-20 hectares) or isolation from other prairies. Conservation Needs The Northern Harrier is a species of special concern in Michigan and is considered threatened or endangered in 12 northcentral and northeastern states (Currier 2001). The declines of Northern Harriers between MBBA I and MBBA II validate the bird’s “Special Concern” status and call for further monitoring. Of particular concern are the declines in areas identified by Yunger (1991) as centers of abundance for Northern Harriers in Michigan. Populations are directly tied to the availability of suitable habitats and the loss of both wetland and grassland habitats undoubtedly contribute to this decline, yet other factors may play a role (e.g. invasive species like Purple Loosestrife and Phragmites spp.). More research is necessary to determine the probable causes of the declines and allow for the development of better management strategies. Without improved management, what was once Michigan’s most common raptor (Barrows 1912) may soon be absent from many regions of the state.


Gerald R. Urquhart

Northern Harrier (Circus cyaneus) Status: Special Concern (MNFI) Literature Cited Barrows, W.B. 1912. Michigan Bird Life. Special Bulletin. Michigan Agricultural College. Lansing, Michigan, USA. Bent, A.C. 1937. Life Histories of North American Birds, Part 1. Dover Publications, New York, New York, USA. Bildstein, K.L. 1988. Northern Harrier (Circus cyaneus). Pages 251-303 in R.S. Palmer, editor. Handbook of North American Birds 4. Yale University Press, New Haven, Connecticut, USA. Bollinger, E.K., P.B. Bollinger and T.A. Gavin. 1990. Effects of hay-cropping on eastern populations of the bobolink. Wildlife Society Bulletin 18: 142-150. Craighead, J.J., and F.C. Craighead, Jr. 1956. Hawks, Owls, and Wildlife. Stackpole Company and the Wildlife Management Institute, Harrisburg, Pennsylvania, USA. Currier, C. 2001. Special animal abstract for Circus cyaneus (Northern Harrier). Michigan Natural Features Inventory. Lansing, Michigan, USA. Dahl, T.E. and G.J. Allord. 1996. History of wetlands in the conterminous United States. Pages 19-26 in J.D. Fretwell, J.S. Williams, and P.J. and Redman, editors. National Water Summary on Wetland Resources. USGS Water-Supply Paper 2425. US Geological Survey, Washington, D.C., USA. Giuliano, W.M., and S.E. Daves. 2002. Avian response to warm-season grass use in pasture and hayfield management. Biological Conservation 106: 1-9. Herkert, J.R., S.A. Simpson, R.L. Westemeier, T.L. Esker, and J.W. Walk. 1999. Response of Northern Harriers and ShortEared Owls to grassland management in Illinois. The Journal of Wildlife Management 63: 517-523. MacWhirter, R.B., and K.L. Bildstein. 1996. Northern Harrier (Circus cyaneus). Account 210 in A. Poole and F. Gill, editors. The Birds of North America. The Birds of North

Gerald R. Urquhart America, Inc., Philadelphia, Pennsylvania, USA. Simmons, R.P., P. Barnard, and P.C. Smith. 1987. Reproductive Behavior of Circus cyaneus in North America and Europe: a comparison. Ornis Scandinavica 18: 33-41. Yunger, J. 1991. Northern Harrier (Circus cyaneus). Pages 162-163 in R. Brewer, G.A. McPeek, and R.J. Adams, Jr. The Atlas of Breeding Birds of Michigan. Michigan State University Press. East Lansing, Michigan, USA. Suggested Citation Urquhart, G.R. 2011. Northern Harrier (Circus cyaneus). in A.T. Chartier, J.J. Baldy, and J.M. Brenneman, editors. The Second Michigan Breeding Bird Atlas. Kalamazoo Nature Center. Kalamazoo, Michigan, USA. Accessed online at: .
