Northern Harrier

Circus cyaneus Linnaeus

 

 

 

Field Guide IDs:
NG-106; G-70; PE-152; PW-pl 16; AE-pl 309; AW-pl 317; AM(I)-224


Nest
Location
Nest
Type
Eggs &
Mating System
Dev. &
Parental Care
Primary &
2ndary Diet
..
Foraging
Strategy
F
I: 31-32 DAYS
SEMIALTRICIAL 1
SHRUB
< 5 feet
F -M
5 (4-9)
MONOG
(POLYGYN)
F: 30-35 DAYS
MF
SMALL VERTS


BREEDING:

Prairie, savanna, slough, wet meadow, marsh. 1 brood.

DISPLAYS:

Courting male performs series of dives from near stall, including barrel-rolls in multiple U-shaped loops.

NEST:

Flimsy; on slightly elevated ground or in thick veg; of sticks, grass, etc., loosely lined with fine materials.

EGGS:

Bluish-white, usu unmarked, but 10% spotted with browns. 1.8" (47 mm).

DIET:

Esp voles, also birds, snakes, frogs, insects (esp grasshoppers), carrion.

CONSERVATION:

Winters s to n Colombia, n Venezuela, and Barbados. Blue List 1972-86; declining from loss of habitat and effects of pesticides: 20% of eggs showed shell thinning in 1970.

NOTES:

Like owls, has curved, sound-reflecting facial ruff which, with characteristic low (<7') flight, enables location of prey by sound. In 25 year WI study, 25% of nests were associated with polygynous matings, often involving subadult females; increased incidence of polygyny associated with high vole populations. Female feeds and broods young. Females aggressively exclude males from preferred feeding areas in nonbreeding season. Outside of breeding season, roost communally on ground. Formerly known as Marsh Hawk; known as Hen Harrier in Europe.

STANFORD. NOTES:

ESSAYS:

Blue List; Eye Color; Raptor Hunting; Polygyny; DDT; Size and Sex in Raptors

REFERENCES:

Brown and Amadon, 1968; Hamerstrom et al., 1985; Rice, 1982; Temeles, 1986.

Except for Stanford Notes, the material in this species treatment is taken, with permission, from The Birder's Handbook (Paul Ehrlich, David Dobkin, & Darryl Wheye, Simon & Schuster, NY. 1988).