BIOLOGICAL DATA AND HABITAT REQUIREMENTS
WILDLIFE SPECIES: Circus cyaneus | Northern Harrier 



TIMING OF MAJOR LIFE HISTORY EVENTS : 
Age of Maturity - 1 year
Mating/Nesting - March through June beginning in the south and moving
                 north; can mate for life, but sometimes males are
                 polygamous; can nest 4 pairs/sq mile in good habitat
Clutch - 4 to 6 eggs
Incubation - 24 to 39 days
Fledge - 30 to 35 days
Life Span - 12 years
Migration - move north beginning in February; move south by late
            November [7,9,16]


PREFERRED HABITAT : 
Northern harriers prefer sloughs, wet meadows, marshlands, swamps,
prairies, plains, grasslands, and shrublands [8].  They nest on the
ground, usually near water, or in tall grass, open fields, clearings, or
on the water.  In the latter case, nests are built on a stick
foundation, willow clump, or sedge tussock [8].  Northern harriers
prefer low perches such as fence posts or stumps.  For hunting, they use
large forest openings.  They occur from sea level to 10,400 feet (3,200
m) in elevation [17].


COVER REQUIREMENTS : 
Northern harriers need open, low woody or herbaceous vegetation for
nesting and hunting [8].  Harriers usually nest adjacent to hunting
grounds and where nest predation is low.  Their food base should be
within 11.2 miles (18 km) of thier nests [21].  They use disproportionate
amounts of rank grasses, sedges (Carex spp.), willows (Salix spp.),
goldenrod (Solidago spp.) and nettle (Urtica spp.) for nest building
relative to the abundance of those plant genera [16].  In Massachusetts,
northern harriers nest in mixed stands of shining sumac (Rhus
copallina), Virginia rose (Rosa virginiana), pasture rose (R. carolina),
northern arrowwood (Viburnum recognitum), and highbush blueberry
(Vaccinium corymbosum) [5].
 


FOOD HABITS : 
The primary prey base of northern harriers is meadow voles (Microtus
pennsylvanicus) [8,16].  They also eat a variety of amphibians,
reptiles, and invertebrates when these food sources are abundant [16].
Other prey includes hares (Lepus spp.), rabbits (Sylvilagus spp.),
shrews (Sorex spp.), ground squirrels (Spermophilus spp.), lesser
prairie chickens (Tympanuchus pallidicinctus), passerine birds, and
occasional carion [7,14,16].


PREDATORS : 
Predators of northern harriers include red fox (Vulpes vulpes), striped
skunk (Mephitis mephitis), raccoons (Procyon lotor), feral cats (Felis
domesticus), mink (Mustela vison), and ravens, crows, and magpies
(Corvids) [21].


MANAGEMENT CONSIDERATIONS : 
Northern harrier nests are often trampeled by grazing cattle.
Suggestions for limiting livestock impact on nesting success include:
fence off nesting areas from livestock, provide more watering sites to
prevent congestion near nests, and reduce stocking rates [3].  Livestock
grazing and haying can also reduce the small mammal population on which
northern harriers depend [6].


REFERENCES : 
NO-ENTRY

Related categories for Wildlife Species: Circus cyaneus | Northern Harrier