Species: Circus cyaneus

Northern Harrier

Species

Birds

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Salish Sea-reliant birds

Terrestrial vertebrates: birds

Encyclopedia of Puget Sound

EGGS: Eggs are pale blue at laying and turn white in a few days; brown markings may occur (Hamerstrom 1969).

Classification

Kingdom

Animalia

Phylum

Craniata

Class

Aves

Order

Falconiformes

Family

Accipitridae

Genus

Circus

NatureServe

Source:
ELEMENT_GLOBAL.2.103344

Classification

Other Global Common Names

Gavilán Rastrero - Marsh Hawk - busard Saint-Martin

Informal Taxonomy

Animals, Vertebrates - Birds - Raptors

Formal Taxonomy

Animalia - Craniata - Aves - Falconiformes - Accipitridae - Circus -

Ecology and Life History

EGGS: Eggs are pale blue at laying and turn white in a few days; brown markings may occur (Hamerstrom 1969).

Short General Description

Slender, medium sized hawk, 46-50 cm (18-20 in.) with a wingspan of 102-118 cm (40-46 in.). Low-flying; wings held in a strong 'V' during flight (MacWhirter and Bildstein 1996). Adult male is gray on the back with a lighter underside, black wingtips, and white rump. Adult female is larger than male, brown on the back with a brown and white (buff) striped underside, and white rump. Juvenile is similar to adult female with a darker brown back and russet underside.

Migration

false - true - true - RECOVERIES: Hammond and Henry (1949) banded 150 nestling harriers in North Dakota and received returns on 12 (8%). The birds had dispersed in a general southern direction, with recoveries from North Dakota (one), Kansas (one), Texas (six), Louisiana (one), Mexico (one), and British Columbia (one). More than half the birds were recovered within one year (seven of 12). Between 1959 and 1977, 12 returns were received from harriers banded as nestlings on the Buena Vista Marsh in Wisconsin (F. Hamerstrom, pers. comm., cited by Beske 1982). The birds had migrated in a general south-southeasterly direction and all were recovered during their first fall and winter. Returns were from the following states: Wisconsin (one), Michigan (two), Illinois (two), Tennessee (one), Mississippi (one), Alabama (one), Georgia (one), Florida (one), South Carolina (one), and North Carolina (one).

Non-migrant

false

Locally Migrant

true

Food Comments

Depending on availability, eats small mammals (especially voles and cotton rats), small and medium-size birds (especially passerines), and some reptiles, amphibians, large insects, carrion. Hunts over open land or marshes; usually flies low when hunting, captures prey on ground.(Palmer 1988) During the breeding season, young are fed primarily small mammals and birds. In Pennsylvania, a variety of birds, mostly juvenile, were important prey for the young, and included northern flickers (Colaptes auratus), eastern meadowlarks (Sturnella magna), red-winged blackbirds (Agelaius phoeniceus), bobolinks (Dolichonyx oryzivorus), American robins (Turdus migratorius), and mourning doves (Zenaida macroura) (Randall 1940). Other prey taken were several species of mice (Microtus, Peromyscus, and Zapus spp.), frogs (Rana spp.), and garter snakes (Thamnophis sirtalis). In New Hampshire, microtine rodents and small and medium-sized birds were the most common prey of harriers (Serrentino 1987). When prey could be identified, the following were noted; shorttail shrew (Blarina brevicauda), meadow vole (Microtus pennsylvanicus), meadow jumping mouse (Zapus hudsonius), ruffed grouse (Bonasa umbellus), northern flicker, American robin, bobolink, and garter snake. In a population breeding on the barrier beaches of Long Island, New York, the meadow vole was the primary prey, with avian species being of secondary importance (England 1989). Waders and passerine birds were the avian groups represented in greatest frequency in prey remains. Small mammals and birds were also the most important prey taken in other North American studies (Breckenridge 1935, Hecht 1951, Craighead and Craighead 1956, Toland 1985). Harriers in New Brunswick concentrated on meadow voles early in the breeding season, with juvenile birds becoming the most common prey item during the mid and late nestling stages (Barnard et al. 1987). In Michigan and Ohio, prey taken in winter consisted primarily of meadow voles (Craighead and Craighead 1956, Bildstein 1978). In Pennsylvania, several rodent species (Microtus, Peromyscus, and Zapus spp.), cottontail rabbits (SYLVILAGUS spp.), and birds were common in the fall and winter diets of harriers (Randall 1940). At a freshwater marsh in Florida, the birds preyed primarily on cotton rats (Collopy and Bildstein 1987). Godfrey and Fedynich (1987) reported that harriers appeared to take waterfowl opportunistically in Texas. During the breeding season, high prey densities have been associated with increased breeding success (Hamerstrom et al. 1985, Simmons et al. 1986). The number of breeding harriers increased during periods of high meadow vole abundance in Wisconsin (Hamerstrom 1979, Hamerstrom et al. 1985) and New Brunswick (Simmons et al. 1986). Hamerstrom et al. (1985) noted that nesting success showed a slightly positive relationship with vole abundance. In New Brunswick, clutch size was positively correlated with vole indices and high provisioning rates by males were associated with an increase in the number surviving to fledging (Simmons et al. 1986). The starvation of nestlings was more common during vole population lows. Harrier density and distribution may be affected by prey abundance during the winter. The number observed at winter roosts increased during winters when meadow vole abundance was high (Weller et al. 1955, Craighead and Craighead 1956). Bildstein (1979) also observed that the placement of roost sites was related, in part, to the density of prey in the surrounding areas. Roost sites were commonly situated in the center of the birds' hunting areas.

Reproduction Comments

BREEDING CHRONOLOGY: Spring arrival dates on breeding grounds in the Northeast range from mid-March to early April, and laying dates range from mid-April to mid and late June (Bent 1937, Hall 1983, Laughlin and Kibbe 1985). Clutches are laid over a period of about nine days, with eggs being laid at two-day intervals (Hamerstrom 1969). Clutch size usually varies from four to six eggs (Bent 1937, Hamerstrom 1969, Duebbert and Lokemoen 1977). Incubation is 30-32 days and begins before the last egg is laid; as a result, hatch is asynchronous (Breckenridge 1935, Hamerstrom 1969). The nestling period varies from 30-41 days (Urner 1925, Hamerstrom 1969, England 1989). Juveniles stay near the nest and are dependent on their parents for food for an additional three to four weeks (Breckenridge 1935, Hamerstrom 1969). COURTSHIP AND BREEDING BEHAVIOR: The distinctive courtship flight has been called a "sky dance." The flight is performed by the male, and occasionally by the female, and consists of a series of nose dives or U-shaped dives (Bent 1937). Hamerstrom (1986) illustrated the behavior as a series of circular flights when viewed from the front. Copulation occurs either on the ground or on a short perch (Brown and Amadon 1968, Clark 1972). The female apparently solicits the male with the begging or food call. Harriers do not appear to mate for life (Hamerstrom 1969). Both sexes may breed in their first year (Watson 1977); however, more females usually breed as yearlings than males (Hamerstrom et al. 1985, England 1989). In Wisconsin, the majority of females bred at one year of age (Hamerstrom et al. 1985). The number breeding as yearlings (both males and females) in Wisconsin (Hamerstrom et al. 1985) and New Brunswick (Simmons et al. 1986) increased during periods of high meadow vole abundance. Although the male, female, or both may choose the nest site, the female appears to do the majority of nest building. Both parents bring nest material (Watson 1977, Toland 1985). The nest is built on the ground and is composed of dead grasses, weeds, and small twigs (Urner 1925, Bent 1937, Hecht 1951). Nests are frequently placed in dense vegetation (Duebbert and Lokemoen 1977, Hamerstrom and Kopeny 1981, Toland 1985, Serrentino 1987). Larger and deeper nests are often built in wet or flood-prone areas (Urner 1925, Sealy 1967). Sealy (1967) measured 12 nests in upland and wetland habitats; depths of nests ranged from 5.0-24.0 centimeters, and diameters varied from 39.0-63.0 centimeters. Harriers may use the same patch of shrubs, field, or general area for several years (Sealy 1967, Balfour and Cadbury 1979, Serrentino 1987, England 1989). Incubation and feeding of the young is done by the female only (Hamerstrom 1969). During incubation and the early portion of the nestling stage, the female rarely leaves the nest. At this time she is supplied with food by the male, accomplished by a "food pass" in which the male drops the prey to her in mid-air over or near the nest (Breckenridge 1935, Hecht 1951). When she is absent, he drops the prey into the nest and usually leaves immediately (Breckenridge 1935). When the nestlings are about two weeks old, the female leaves the nest to hunt more frequently (Hecht 1951, Schipper 1973). NESTLING DEVELOPMENT: Newly-hatched harriers are covered with a layer of white down. Their eyes open a few hours after hatching. Mean weight at hatching is 19.8 grams (Scharf and Balfour 1971). For the first five days, the nestlings are almost continually brooded by the female (Hecht 1951). Between two and three weeks of age the young begin to make tunnels in the vegetation adjacent to the nest. These tunnels may be used as escape routes (Balfour and MacDonald 1970). Between the third and fourth weeks, the young lose most of their down and acquire their distinctive juvenal plumage (Watson 1977). The young are usually able to fly at 30 days, and have become fairly proficient flyers at 35 days (Hammond and Henry 1949). The lightest individuals and those with the most well developed flight feathers, usually the males, fledge first (Scharf and Balfour 1971). Because hatching occurs asynchronously, the nest contains young of varying sizes. The smallest nestlings often do not survive because of competition for food with their larger nest-mates (Breckenridge 1935, Balfour and MacDonald 1970). Female nestlings are larger than males for most of the nestling period (Scharf and Balfour 1971, Picozzi 1980). LONGEVITY: The average life span is approximately seven years in the wild (Brown and Amadon 1968). The longest life span of a banded, free-ranging, individual was 16 years, 5 months (Clapp et al. 1982). Juvenile mortality has been attributed to starvation and malnutrition (Craighead and Craighead 1956). In Great Britain, mortality was highest for first-year birds (Balfour and Cadbury 1975, Watson 1977). In the Orkney Islands, survival of hen harriers increased from 32% in the first year to 70% in the following year (Balfour and Cadbury 1975). NESTING SUCCESS: Hatching success varies greatly both among years and study areas. In Michigan, yearly hatching success varied from 0-78% (Craighead and Craighead 1956) and in Canada from 23-89% (Sealy 1967). Fledgling production, i.e., the number of young fledged per female (monogamous females only) varied as follows: 1.5-2.3 for all nests, including those that failed (Craighead and Craighead 1956, Picozzi 1978, Balfour and Cadbury 1979, Hamerstrom et al. 1985, England 1989), and 2.7-3.1 for successful nests (Picozzi 1978, Balfour and Cadbury 1979, Hamerstrom et al. 1985, England 1989). For data on fledgling production for polygynous females, see Balfour and Cadbury (1979), Hamerstrom et al. (1985), Simmons et al. (1986), and England (1989). The frequency of renesting after nest failure is low. Renesting has been documented in populations studied in New Brunswick (Simmons 1984), Michigan (Craighead and Craighead 1956), and the Dakotas (Duebbert and Lokemoen 1977). In Wisconsin (Hamerstrom 1969) and New York (England 1989), harriers did not lay replacement clutches. In Wisconsin, the adults left the study area within 24 hours of nest failure (Hamerstrom 1969). POLYGYNY: Polygyny has been well documented (Breckenridge 1935; Hecht 1951; Clark 1972; Balfour and Cadbury 1979; Hamerstrom et al. 1985; Simmons et al. 1986; England 1989). In mainland Scotland, the frequency of polygynous matings was low (Picozzi 1978). However, in the Orkney Islands in Scotland, polygyny accounted for a majority of the mating associations in some years (Balfour and Cadbury 1975, Balfour 1979; Picozzi 1984). In Wisconsin and New Brunswick, the occurrence and frequency of polygyny was related to meadow vole abundance. High vole numbers led to increases in (1) the numbers nesting, (2) the number of yearlings nesting, and (3) the occurrence of polygyny. Simmons et al. (1986) concluded that the frequency of polygynous matings increased during high vole years because males were able to provision more females successfully. In the Orkney Islands and on Long Island, New York, the occurrence of polygyny was related to an unbalanced sex ratio that resulted in a shortage of male breeders (Picozzi 1984, England 1989). Balfour and Cadbury (1979) noted that polygyny was fairly rare until the 1950s, when the population began to increase from a low point. Between the 1950s and 1960s more females than males were reared in the population (Picozzi 1984); during recent years, more males than females have fledged.

Ecology Comments

NONBREEDING: May aggregate in communal roosts in winter in areas of high prey density (Evans 1982; see also Palmer 1988). In winter, may hunt in same area for several consecutive days (see Palmer 1988). In the nonbreeding season, females may defend preferred feeding areas against males. Vegetation structure affects harrier habitat selection and hunting behavior. Harriers often increase flight altitude with increasing vegetation height, enabling them to "see" into the vegetation (Schipper 1977, Serrentino 1987). In a freshwater marsh in Florida, harrier hunting success was negatively affected by the dense marsh grasses that concealed their primary prey, the cotton rat (SIGMODON HISPIDUS) (Collopy and Bildstein 1987). BREEDING DENSITY AND DISPERSION: Breeding density about 0.8-6.4 females per ten square kilometers (see Serrentino 1992). Breeding density and dispersion of are affected by the abundance of prey species (Hamerstrom 1979), the occurrence of polygyny (Balfour and Cadbury 1979, Simmons et al. 1986), nest site fidelity (Sealy 1967, Balfour and Cadbury 1979), and habitat quality (Picozzi 1984, Simmons and Smith 1985). The number of nesting harriers increases during high meadow vole abundance in those populations that prey primarily on voles (Hamerstrom 1969, 1979; Clark 1972; Simmons et al. 1986). In Wisconsin (Hamerstrom 1979) and New Brunswick (Simmons et al. 1986), nest densities increased more than twofold when vole abundance rose from low to high. Polygyny tends to increase the degree of nest clumping in breeding populations (Balfour and Cadbury 1979, Simmons et al. 1986, England 1989). In Orkney, the distance between nests decreased with increasing harem size (Picozzi 1984). Harriers often occupy the same nest sites or nesting territories, but not the nest itself, for several years (Sealy 1967, Balfour and Cadbury 1979, Serrentino 1987, England 1989). In New Hampshire, a pair nested in the same field for a minimum of five years (Serrentino 1987). Both Picozzi (1984) and Simmons and Smith (1985) noted that high densities of breeding harriers in some areas were probably a reflection of habitat quality. At a moorland site in mainland Scotland (Picozzi 1978), nest densities were much lower than densities on the Orkney Islands (Balfour and Cadbury 1979). Differences between the two areas included an abundance of prey in the farmlands and wetlands at Orkney (Picozzi 1984). Simmons and Smith (1985) postulated that harrier nest densities at a predominantly wet marsh in New Brunswick were higher than those reported in other areas because of increased availability of nest sites and high densities of meadow voles. HUNTING RANGE SIZE: The sizes of hunting ranges vary widely during the breeding season in different areas, presumably because of differences in habitat types, availability of prey species, distribution of nest sites, and stage of the breeding cycle (Craighead and Craighead 1956, Balfour and MacDonald 1970, Balfour and Cadbury 1979, Serrentino 1992). In two midwestern studies, the range sizes for pairs varied from 2.6-5.5 kilometers squared (Breckenridge 1935, Craighead and Craighead 1956). Males usually have larger hunting ranges than females (Hecht 1951, Schipper 1977, Watson 1977). Schipper (1977) reported range sizes from 1.8-12.3 kilometers squared for males in the Netherlands, and Martin (1987) observed range sizes from 9.7-17.7 kilometers squared for males in Idaho. Hunting range sizes of approximately 0.8-5.4 kilometers squared for females were observed in both the Netherlands and New Hampshire (Schipper 1977, Serrentino 1987). In North Dakota, breeding harriers were found only in grassland patches greater than 100 hectares, and were encountered in large patches more often than statistically expected (Johnson and Igl 2001). Little data are available on the range sizes of nonbreeding harriers. In Michigan, wintering birds flew up to eight kilometers from roost sites to hunting ranges (Craighead and Craighead 1956). The number hunting in a particular area decreased with increasing distance from the roost, and hunting range size varied from 0.12-2.6 kilometers squared. In the Netherlands, appeared to have fixed hunting ranges of unidentified sizes (Schipper et al. 1975). WEATHER: Cold or rainy weather may negatively affect breeding success. Egg-laying may be delayed by cold weather (Watson 1977, Schipper 1979). Prolonged periods of rainy weather, particularly during the incubation and nestling stages, may cause nest desertion or death of nestlings from exposure (Follen 1986, Simmons et al. 1986). Abnormally high tides have destroyed nests in coastal areas (Dunne 1986). PARASITES: Raptors are susceptible to a number of bacterial and viral diseases. Numerous species of endoparasites, blood protozoans, and ectoparasites have been recorded in raptors. Little is known of the effects of diseases and parasites on wild populations because of the scarcity of data and the difficulty associated with separating the direct causes of death from diseases and parasites with the indirect causes (e.g., birds weakened by disease may succumb to death from predation, starvation and severe weather) (Newton 1979). External and internal parasites have been found on free-living northern harriers (Peters 1936, Scharf 1966, Hamerstrom 1969, Anderson and Freeman 1969, Pence 1973).

Length

Weight

531

Conservation Status

NatureServe Global Status Rank

Global Status Last Reviewed

2008-01-03

Global Status Last Changed

1996-11-22

Distribution

Conservation Status Map

Global Range

H - >2,500,000 square km (greater than 1,000,000 square miles) - H - Breeding range in North America extends 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 (and formerly Florida). In Eurasia, breeding occurs from the British Isles, Scandinavia, northern Russia, and Siberia south to the Mediterranean region, southern Russian, Turkestan, Amurland, Ussuriland, Sakhalin, and the Kurile Islands (AOU 1998). The species breeds rarely or erratically south of the North American breeding range (MacWhirter and Bildstein 1996). Breeding range is large but often highly discontinuous. During the nonbreeding season in North America the range extends from southern Canada or the northern contiguous United States south through the United States, Middle America, and the Antilles to northern Colombia, Venezuela, and Barbados; casual or accidental in Hawaii (AOU 1998, MacWhirter and Bildstein 1996). In North America, northern harriers winter in largest numbers in the Great Basin and central and southern Great Plains (Root 1988). The coastal areas of New York, New Jersey, Delaware, Maryland, and Virginia support the highest number of wintering birds in the Northeast (National Audubon Society 1971-74, 1982-83, 1985-87). During the nonbreeding season in Eurasia the range extends from the British Isles, southern Scandinavia, and southern Japan south to northwestern Africa, Asia Minor, India, Burma, eastern China, and the Ryukyu Islands (AOU 1998).

Global Range Code

Global Range Description

>2,500,000 square km (greater than 1,000,000 square miles)

ELEMENT_GLOBAL.2.103344