Northern Harrier

NORTHERN HARRIER

Photo Credit: Bill Horn
http://www.birdsofoklahoma.net/index.html

SCIENTIFIC NAME: Circus cyaneus (Linnaeus)

OTHER NAMES: Blue Hawk (male), Frog Hawk, Hen Harrier, Marsh Harrier, Marsh Hawk, Mouse Hawk, White-rumped Hawk (Terres 1980).

DESCRIPTION: A medium-sized (43-58 cm [17-23 in.]; Nat. Geog. Soc. 1987), slim, long-tailed, long-legged hawk with a characteristic facial ruff that gives it an owl-like appearance. Sexes dichromatic, but both have conspicuous white rump patches. Adult male pale gray above and white below with reddish spots on underparts; wingtips edged in black. Adult female 12.5 percent larger and 50 percent heavier than male; predominantly dark brown above, light buffy below, with some streaking on underparts. Immatures resemble females; brown above, but reddish below (MacWhirter and Bildstein 1996). During courtship, both sexes emit a rapid series of kek or quik notes. Distress call similar, but given at higher pitch. Two subspecies recognized: larger northern harrier (Circus cyaneus hudsonius) and Eurasian hen harrier (C. c. cyaneus ) (MacWhirter and Bildstein 1996).

DISTRIBUTION: Breeding distribution large, but often highly discontinuous. In North America, occurs from northern Alaska to northern Saskatchewan and southern Quebec, south to northern Baja California, southern Texas, southern Missouri, West Virginia, southeastern Virginia, and North Carolina (formerly found in Florida). Wintering distribution in North America from southern Canada or the northern contiguous United States south through the United States, Central America, and the Antilles to northern Colombia, Venezuela, and Barbados (AOU 1998). In Alabama, fairly common in winter, spring, and fall in all regions of Alabama (Jackson 2001a).

HABITAT: Breeds in open wetlands, including marshy meadows; wet, lightly grazed pastures; old fields; freshwater and brackish marshes; also dry uplands, including upland prairies, mesic grasslands, drained marshlands, croplands, cold desert shrub-steppe, and riparian woodlands. In both wetland and upland areas, densest populations typically associated with large tracts of undisturbed habitats dominated by thick ground vegetation. Wintering birds use a variety of open habitats dominated by herbaceous cover, including deserts, coastal sand dunes, dry plains, upland and lowland grasslands, salt- and freshwater marshes, croplands, pasturelands, abandoned fields, and open-habitat floodplains. Select habitats on the basis of availability and abundance of prey (MacWhirter and Bildstein 1996).

LIFE HISTORY AND ECOLOGY: Return to breeding grounds in March or April. Males establish territories and a monogamous pair bond often formed; however, simultaneous polygyny also reported. Nest is a platform of dry sticks, straws, weed stems, and grasses built primarily by female on ground, commonly near low shrubs, in tall weeds or reeds, sometimes in bogs (Terres 1980). A clutch of three to nine (usually five) white eggs laid in March-June. Females incubate eggs for 30-32 days, with young flying about 30-41 days after hatching (Serrentino et al. 1998). Male provides food to female during incubation and until young are 10-14 days old. Young become independent around 6.5-9.5 weeks after hatching (MacWhirter and Bildstein 1996). When hunting, usually flies low (3-10 m [10-33 ft.]) over ground, with a few wingbeats followed by a short glide with wings held up in a shallow V. Depends heavily on auditory and visual cues to locate prey such as small rodents, shrews, small birds, and insects. Roosts on ground, very often communally, outside the nesting season (MacWhirter and Bildstein 1996).

BASIS FOR STATUS CLASSIFICATION: Christmas Bird Count and Breeding Bird Survey data indicate population declines in North America in twentieth century. Declines primarily attributed to habitat degradation (e.g., draining of wetlands, monotypic farming, and reforestation of farmlands) (MacWhirter and Bildstein 1996). Small mammals, their primary prey, prefer abandoned fields and other disturbed habitats with vegetation cover consisting of dense grasses and weeds. In contrast, extensive croplands and hayfields that are subject to several annual cuttings may depress small mammal populations (Serrentino et al. 1998). North American populations also negatively affected by organocholorine pesticides. A mean decrease of 15 percent in eggshell thickness of eggs was noted between 1947 and 1969. Declines of both breeding and migrating harriers and occurrence of behavioral changes coincided with heavy use of DDT (MacWhirter and Bildstein 1996, Serrentino et al. 1998). Priority designation in Alabama based on Partners In Flight scores for relative abundance, threats to breeding populations, and population trend. Occurs in low relative abundance in all parts of breeding and wintering distribution. Severe deterioration in future suitability of breeding conditions in Appalachian Mountains, Central Hardwoods, and Piedmont is expected. Christmas Bird Count data suggest a moderate decrease of wintering populations in all four bird conservation regions that occur in Alabama (PIF 2002).

Author: Paul D. Kittle