BioKIDS - Kids' Inquiry of Diverse Species, Circus cyaneus, northern harrier, marsh hawk: INFORMATION

What do they look like?

Northern harriers have several characteristics which distinguish them from other birds. Feathers around their face in the shape of a disk focus sound into their ears. Their wings form a v-shape during flight. They also have a white rump which is visible during flight. (Wheeler and Clark, 1987)

Adult harriers have yellow eyes. Males are gray on their back side. On the front they are white with darker spots on their chests and black tips on their wings. Adult females are brown with white strips on the undersides of their wings. Immature harriers resemble adult females, bt they are a darker shade of brown with a rusty colr underneath. Immature harriers have brown eyes. (Wheeler and Clark, 1987; Wheeler and Clark, 1987)

The length of adult males varies between 41 and 45 cm (16 to 18 in). The length of adult females varies between 45 and 50 cm (18 to 20 in). Typically the wingspan of adult males varies between 97 and 109 cm (38 to 43 in). The wingspan of adult females varies between 111 and 122 cm (44 to 48 in). The weight of adult males is approximately 290 to 390 grams(1/2 to 1 lb). The average weight of adult females is approximately 390 to 600 grams(1 to 1.3lbs). (Wheeler and Clark 1995,Weidensaul 1996,Ryser 1985,Wheeler and Clark 1987) (Wheeler and Clark, 1987)

Other Physical Features
endothermic
homoiothermic
bilateral symmetry

Sexual Dimorphism
female larger
sexes colored or patterned differently

Range mass

290 to 600 g

10.22 to 21.15 oz
Range length

41 to 50 cm

16.14 to 19.69 in
Range wingspan

340 to 384 mm

13.39 to 15.12 in

Where do they live?

Northern harriers are found throughout the northern hemisphere. In the Americas (the Nearctic) they breed throughout North America from Alaska and much of Canada to as far south as Baja California, New Mexico, Texas, Kansas, and North Carolina. They are only rarely seen breeding in parts of the Atlantic coastal states, such as Vermont, Rhode Island, and Maine and are also rare in the arid and mountainous western regions, including most of California, Oregon, and Washington. Their winter range is from southern Canada to the Caribbean and Central America. (Macwhirter and Bildstein, 1996)

In the Palearctic, northern harriers breed throughout Eurasia, from Portugal in the west, to Lapland and Siberia in the north, and east through China. They winter in northern African and tropical Asia. (Macwhirter and Bildstein, 1996)

Biogeographic Regions
nearctic
- native
palearctic
- native
oriental
- native

Other Geographic Terms
holarctic

What kind of habitat do they need?

Northern harriers are found mainly in open habitats such as fields, savannas, meadows, marshes, upland prairies, and desert steppe. They also occur in agricultural areas and riparian zones. Densest populations are found in large expanses of undisturbed, open habitats with dense, low vegetation. In eastern North America northern harriers are found most frequently in wetland habitats. In western North America they are most abundant in upland habitats such as desert steppe. Northern harriers avoid forested and mountainous areas. (Eastman, 1999; Macwhirter and Bildstein, 1996; Wheeler and Clark, 1987)

These animals are found in the following types of habitat
temperate
tropical
terrestrial

Terrestrial Biomes
savanna or grassland
chaparral

Wetlands
marsh

Other Habitat Features
agricultural
riparian

How do they reproduce?

Adult males show interesting behaviors during mating season. During this time the male courts the female by flying high into the air and then diving down. Males generally have between 1 and 3 mates.During incubation of the eggs the male provides food for the female, but he stays away from the nest. When he is near the nest he will call out, and when the female comes to him he will drop food to her. During breeding season, northern harriers become very territorial and will attack anyone who threatens their nesting areas. (Burton and Burton, 1989; Chinery, 1992; Eastman, 1999; Ryser, 1985)

Most males are monogamous, which means they mate with only one females, but some have been known to mate with up to 5 females in one season. Females only mate with one male per season.

Mating System
monogamous
polygynous

Eggs are laid from mid-May to early June. They are white with a blue tint, and occasionally have brown spots. The eggs are approximately 47 x 36mm. Three to five eggs are laid, and incubation is only by the female. (Baicich and Harrison, 1997; Burton and Burton, 1989; Eastman, 1999; Terres, 1980; Wheeler and Clark, 1987)

The eggs hatch in approximately 31 to 32 days. Male harriers will contribute to the feeding of their offspring during the time they are in the nest and will watch over the nest for a maximum of 5 minutes when the female is away. (Baicich and Harrison, 1997; Burton and Burton, 1989; Eastman, 1999; Terres, 1980; Wheeler and Clark, 1987)

Key Reproductive Features
iteroparous
gonochoric/gonochoristic/dioecious (sexes separate)
sexual
oviparous

How often does reproduction occur?

Northern harriers breed once per season.
Breeding season

Primary females breed from April through July, while secondary females breed from May through September.
Range eggs per season

3 to 5
Average eggs per season

4.4
Average eggs per season

5

AnAge
Range time to hatching

28 to 36 days
Range fledging age

30 to 35 days
Average age at sexual or reproductive maturity (female)

2 years
Average age at sexual or reproductive maturity (female)
Sex: female

365 days

AnAge
Average age at sexual or reproductive maturity (male)

3 years
Average age at sexual or reproductive maturity (male)
Sex: male

365 days

AnAge

The female is the primary caregiver for young northern harriers. She shelters them from the weather with her wings. She also feeds her young by taking food from the male when they are young, and later, by passing the food to them while in flight. The male northern harrier brings food for his mate and offspring, but leaves them when the hatchlings are about two weeks old. (Macwhirter and Bildstein, 1996; Macwhirter and Bildstein, 1996; Macwhirter and Bildstein, 1996)

Parental Investment
altricial
pre-fertilization
- provisioning
pre-hatching/birth
- provisioning
  - male
  - female
- protecting
  - male
  - female
pre-weaning/fledging
- provisioning
  - male
  - female
- protecting
  - female
pre-independence
- provisioning
  - female
- protecting
  - female

How long do they live?

There is very little information known concerning the lifespan of northern harriers. The longest lifespan reported is 16 years and 5 months. The average lifespan, however, is 16.6 months. The oldest reported breeding female was 8 years old.

Range lifespan
Status: wild

16.19 (high) years
Average lifespan
Status: wild

16.6 months
Average lifespan
Status: wild

197 months

Bird Banding Laboratory

How do they behave?

Besides flying, northern harriers walk and hop. They use this method of locomotion while retrieving prey, collecting nesting materials, and retrieving nestlings that have strayed from the nest. (Macwhirter and Bildstein, 1996; Macwhirter and Bildstein, 1996)

Harriers typically fly slow and low to the ground, gliding often, and sometimes seeming to hover. They occasionally soar. Males fly faster and are more agile in flight than either females or juveniles and have been seen overtaking prairie falcons. (Macwhirter and Bildstein, 1996; Macwhirter and Bildstein, 1996)

Northern harriers may nest alone or in loose assemblages. Territorial behavior is minimal especially during the breeding season, except at the nest site where both males and females will defend their territory against conspecific intruders. In winter, however, females aggressively exclude males from prime feeding territories. Despite this strong territoriality on the part of females, individuals of both sexes roost on the ground communally during the non-breeding season. During migration, northern harriers, like other raptors, prefer not to fly over open water. (Macwhirter and Bildstein, 1996)

Northern harriers are active during the day and spend much of their time hunting.

Key Behaviors
flies
glides
diurnal
motile
migratory

Range territory size

1.7 to 150 km^2

Home Range

During breeding season both sexes tend to be territorial around the nests, but otherwise, home ranges tend to overlap. Monogamous male territories tend to be approximately 260 ha (2.6 km square) in size, ranging from 170 (1.7 km square) to 15,000 (150 km square) ha. (Macwhirter and Bildstein, 1996)

How do they communicate with each other?

Northern harriers are most vocal near the nest. When mating, they make fast kek, quik, and ek sounds. When they are in distress, harriers make rapid high-pitched sounds. Males have a more nasal sound than females. (Macwhirter and Bildstein, 1996)

Females issue a call for food, most often during mating season. It is a piercing eeyah, eeyah sound which can last for several minutes. Males respond to this with a purrduk sound that can barely be heard. In response to this sound the female will leave her nest to receive food. (Macwhirter and Bildstein, 1996)

Young harriers emit a "begging call" when they see their parents flying overhead or when they hear their parents call out to one another. This sound is called a pain call, and is a series of chit notes. (Macwhirter and Bildstein, 1996)

Northern harriers, like most raptors, have a keen sense of vision. Northern harriers are unusual in that their owl-like facial ruff enhances their sense of hearing, which they use extensively in finding prey. (Macwhirter and Bildstein, 1996)

Communication Channels
visual
acoustic

Perception Channels
visual
tactile
acoustic
chemical

What do they eat?

The diet is variable, depending on dominant prey types in the area. In areas with large populations of small mammals, they make up 95% of the diet. In northern grasslands, the diet may be almost exclusively Microtus voles. Northern harriers also eat other small vertebrates, including snakes, frogs, passerine birds, and small waterfowl. When hunting for food, harriers glide at a slow pace close to the ground until prey is found. Harriers then dive quickly to capture it. They may also hide in vegetation, waiting to pounce on prey. They sometimes store extra prey to eat later. (Dechant, et al., 1998; Eastman, 1999; Macwhirter and Bildstein, 1996; Wheeler and Clark, 1987)

Primary Diet
carnivore
- eats terrestrial vertebrates

Animal Foods
birds
mammals
amphibians
reptiles

Foraging Behavior
stores or caches food

What eats them and how do they avoid being eaten?

Northern harriers have many predators, including raccoons, skunks, American crows, common ravens, coyotes, feral dogs, red foxes, and great horned owls. American crows and common ravens prey on eggs, while other raptors, especially great horned owls, target nestlings. (Burton and Burton, 1989; Chinery, 1992; Eastman, 1999; Macwhirter and Bildstein, 1996; Ryser, 1985)

Northern harriers with young generally respond aggressively to predators. Defense ranges from aggressive distress calls to striking the intruder with closed talons. Males and females contribute equally to defense. (Macwhirter and Bildstein, 1996)

Northern harriers often compete with short eared owls for the same food source. Food shortages can occur because both hunt the same prey. Northern harriers have a tendency to steal prey away from short eared owls by harassing them until the owl drops its prey. Short eared owls have been known to hunt both at night and during the day, while northern harriers hunt only during the day. (Burton and Burton, 1989; Chinery, 1992; Eastman, 1999; Ryser, 1985)

Known Predators
- American crow Corvus brachyrhynchos
- common ravens (Corvus corax)
- coyotes (Canis latrans)
- great horned owls (Bubo virginianus)
- feral dogs (Canis lupus familiaris)
- striped skunks (Mephitis mephitis)
- red foxes (Vulpes vulpes)
- raccoons (Procyon lotor)

What roles do they have in the ecosystem?

Predation by northern harriers can have significant effects on populations of field mice and other rodents. (Macwhirter and Bildstein, 1996)

As prey, northern harriers provide food for some terrestrial predators, such as coyotes Canis latrans, striped skunks Mephitis mephitis, raccoons Procyon lotor, and red foxes Vulpes vulpes.

Do they cause problems?

There are no negative affects of northern harriers on humans. (Chinery, 1992; Macwhirter and Bildstein, 1996)

How do they interact with us?

Northern harriers help protect crops by reducing populations of field mice and other rodents. Unlike some other hawk species, they do not attack poultry. (Eastman, 1999; Macwhirter and Bildstein, 1996)

Ways that people benefit from these animals:
controls pest population

Are they endangered?

No conservation measures have been enacted specifically for this species, however, conservation measures for waterfowl and habitat management for game birds has increased local numbers of nesting northern harriers. The species is abundant enough to be rated "Least Concern" by the IUCN. It it protected under the Migratory Bird Treaty, and is listed in Appendix II of CITES. (Macwhirter and Bildstein, 1996)

IUCN Red List

Least Concern
More information
IUCN Red List

Least Concern
More information
US Migratory Bird Act

Protected
US Federal List

No special status
CITES

Appendix II

Contributors

Lauren Pajerski (editor), Undergraduate Research Opportunity Program, University of Michigan, George Hammond (editor), Animal Diversity Web, Tanya Dewey (editor), Animal Diversity Web.

Brian Limas (author), Fresno City College, Carl Johansson (editor), Fresno City College.

References

Baicich, P., C. Harrison. 1997. A Guide to the Nests, Eggs, and Nestlings of North American Birds. New York City, New York, USA: Academic Press.

Burton, M., R. Burton. 1989. Northern harrier. Pp. 1162 in The Marshall Cavendish International Wildlife Encyclopedia, Vol. 10. Toronto, Canada: Marshall Cavendish Corporation.

Chinery, M. 1992. Pp. 144 in The Kingfisher Illustrated Encyclopedia of Animals. New York: Kingfisher Books.

Dechant, J., M. Sondreal, D. Johnson, L. Igl, C. Goldade. 1998. "Effects of management practices on grassland birds: Northern Harrier.." (On-line). Accessed September 15, 2000 at http://www.npwrc.usgs.gov/resource/literatr/grasbird/harrier/harrier.htm.

Eastman, J. 1999. Birds of Lake, Pond, and Marsh. Pennsylvania, USA: Stackpole Books.

Macwhirter, R., K. Bildstein. 1996. Northern Harrier. The Birds of North America, 210: 1-25.

Ryser, F. 1985. Birds of the Great Basin- A Natural History. Reno, Las Vegas: University of Nevada Press.

Snyder, N., H. Snyder. 1991. Birds of Prey- Natural History and Conservation of North American Raptors. MN.: Voyageur Press Inc..

Terres, J. 1980. Pp. 483 in The Audubon Society Encyclopedia of North American Birds. New York: Alfred A.Knoph Inc..

Weidensaul, S. 1996. Raptors-The Birds of Prey. New York: Lyons and Burford.

Wheeler, B., W. Clark. 1995. A Photographic Guide to North American Raptors. San Diego: Academic Press Inc..

Wheeler, B., W. Clark. 1987. The Peterson Field Guide Series- A Field Guide to Hawks of North America. Boston: Houghton Mifflin Company.

Critter Catalog

Additional information:

northern harrier, marsh hawk