Northern Harrier
Circus cyaneus
Summary 7
The Hen Harrier (Circus cyaneus) or Northern Harrier (in the Americas) is a bird of prey. It breeds throughout the northern parts of the northern hemisphere in Canada and the northernmost USA, and in northern Eurasia. This species is polytypic, with two subspecies. Marsh Hawk is a historical name for the American form.
Description 8
Longueur 44-52 cm, envergure 100-120 cm, poids 300-600 g.
Il habite toutes sortes de terrains ouverts, à tendance sèche et à couverture végétale basse (cultures, friches, landes, coupes forestières…). En hiver, il est souvent trouvé dans les cultures, prairies, landes et zones humides. La sélection de l’habitat est gouvernée par la disponibilité de la proie principale.
Le Busard Saint-Martin se nourrit surtout de petits oiseaux et rongeurs saisis par surprise. Il est le plus agile des busards européens et capture (notamment le mâle) plus de proies rapides – passereaux, en particulier – que ses congénères. Lorsqu’il chasse les campagnols, il se déplace lentement (environ 20-30 km/h) et ignore les oiseaux volants, tandis que lorsqu’il chasse les oiseaux, son vol de recherche peut dépasser les 40 km/h. Il arrive qu’il parasite d’autres oiseaux de proie tels que le Busard cendré, le Faucon crécerelle ou le Hibou des marais.
C’est un chasseur solitaire tout au long de l’année, qui peut s’assembler là où les ressources alimentaires abondent (rarement plus de 10 individus ensemble). En hiver, bien que moins sédentaire qu’en saison de reproduction, il tend à fréquenter un territoire individuel, au moins pendant quelques semaines. L’espèce est généralement monogame mais des harems se forment certaines années dans certaines populations. Lors des bonnes années à rongeurs, les nids, normalement très dispersés, peuvent être regroupés en colonies lâches, à quelques centaines de mètres les uns des autres. Le mâle commence à nourrir la femelle dès les premières étapes de construction du nid, puis l’approvisionne entièrement durant l’incubation et les premiers jours de la nichée. Les proies sont souvent passées à la femelle en vol, de façon spectaculaire et en criant.
Le nid est un amoncellement de végétation récoltée alentour (herbes, bruyères, joncs…) dont la hauteur varie selon les sites choisis (jusqu’à 45 cm dans les sites humides). Il est construit au sol dans la végétation épaisse. La ponte de 4 à 6 œufs (maximum 12, mais il peut alors s’agir d’une 2e couvée ajoutée à la 1ère) est déposée à partir de la fin-avril. L’incubation dure environ 1 mois et les jeunes s’envolent à l’âge de 32-42 jours, les mâles étant plus précoces que les femelles.
Distribution 9
Northern harriers are found throughout the northern hemisphere. In the Americas they breed throughout North America from Alaska and Canadian provinces south of tundra regions south as far 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 similarly rare in the arid and mountainous western interior, including most of California, Oregon, and Washington. Their winter range is from southern Canada to the Caribbean and Central America.
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.
Biogeographic Regions: nearctic (Native ); palearctic (Native ); oriental (Native )
Other Geographic Terms: holarctic
Morphology 10
Northern harriers have several characteristics which distinguish them from other birds. Specialized feathers around their face in the shape of a disk focus sound into their ears. Their wings form a dihedral when in gliding flight, and they have a distinctive white rump patch which is obvious during flight.
Adult harriers have yellow eyes. Adult males are gray on their dorsal side. Ventrally, they are white, except for spots on their chest, and black wingtips. Adult females are a brown color, except for underneath their wings, where there are white stripes. Immature males and females resemble the adult female, but they have a darker shade of brown covering the dorsal side and a brownish rusty color underneath. Immature harriers have brown eyes.
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)
Range mass: 290 to 600 g.
Range length: 41 to 50 cm.
Range wingspan: 340 to 384 mm.
Other Physical Features: endothermic ; homoiothermic; bilateral symmetry
Sexual Dimorphism: female larger; sexes colored or patterned differently
Diagnostic description 11
Adults and immatures of both sexes have a distinctive, white rump patch.
Habitat 12
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.
Habitat Regions: temperate ; tropical ; terrestrial
Terrestrial Biomes: savanna or grassland ; chaparral
Wetlands: marsh
Other Habitat Features: agricultural ; riparian
Migration 13
Non-Migrant: No. All populations of this species make significant seasonal migrations.
Locally Migrant: Yes. At least some populations of this species make local extended movements (generally less than 200 km) at particular times of the year (e.g., to breeding or wintering grounds, to hibernation sites).
Locally Migrant: Yes. At least some populations of this species make annual migrations of over 200 km.
Generally arrives in northern breeding areas in March-April (and May in Alaska). Northward migration may continue in an area even after local nesting has begun. Southward migration in the U.S. and Canada occurs August-November. Northern breeders may migrate farther south than do some more sedentary populations breeding at lower latitudes (Palmer 1988). In Costa Rica, arrives in early October, departs by early May (Stiles and Skutch 1989).
During migration, harriers move in a broad front at heights up to 770 m (Kerlinger 1989). They have been observed traveling along both coastal and inland ridges at numerous sites in eastern North America (Nagy 1977, Bildstein et al. 1984, Heintzelman 1986, Dunne and Sutton 1986). Sattler and Bart (1984) stated that harriers may not be as conspicuous as other raptors during migration because of their frequent use of flapping flight versus soaring, and their tendency to migrate individually or in small flocks. Harriers do not appear to avoid crossing water during migration. They have been seen "island hopping" in Maine, and have been observed in Bermuda, the Bahamas, and the West Indies (Bildstein 1988, Kerlinger 1989).
Most of the information on harrier migration comes from the autumn season. In the Northeast, the peak of fall migration occurs during September in Maine (Appell 1986), from the last week in September to the first week in October in Rhode Island (C. Raithel, pers. comm.), and from early October to mid-November in Maryland (Stewart and Robbins 1958). In West Virginia, one or two harriers are usually observed migrating over the eastern mountain ridges from September to early October (Hall 1983). At Hawk Mountain in Pennsylvania, the peak period for harrier migration is October and November, although their entire migratory period ranges from August to November (Broun 1939, Spofford 1969, Nagy 1977). During August and September, immature harriers are the most common, followed by both adults and immatures in varying numbers in October. Adult males are predominant later in the season (Nagy 1977). Using data from four raptor banding stations (Cape May Point and Kittatinny Mountain, New Jersey; Hawk Cliff, Ontario; and Duluth, Minnesota), Bildstein et al. (1984) found similar trends in the timing of migration with respect to sex and age as that observed by Nagy (1977) at Hawk Mountain.
During the spring migration in central Wisconsin, adult males preceded both adult females and immatures, and adult females arrived before immatures at potential breeding areas (Hamerstrom 1969). On Long Island, New York, males also arrived at breeding sites before females (England 1989).
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).
Sources and Credits
- (c) BJ Stacey, some rights reserved (CC BY-NC), http://www.flickr.com/photos/finaticphotography/8391992149/
- (c) Len Blumin from Mill Valley, California, United States, some rights reserved (CC BY), https://upload.wikimedia.org/wikipedia/commons/c/c8/Northern_%28Hen%29_Harrier.jpg
- (c) Kevin Cole from Pacific Coast, USA, some rights reserved (CC BY), https://upload.wikimedia.org/wikipedia/commons/thumb/d/d4/Northern_Harrier_taking_off.jpg/460px-Northern_Harrier_taking_off.jpg
- (c) Blake Matheson, some rights reserved (CC BY-NC), http://farm4.static.flickr.com/3409/3205637928_fdcc82715a_o.jpg
- Kositoes, no known copyright restrictions (public domain), https://upload.wikimedia.org/wikipedia/commons/thumb/8/87/Wow2_filtered.jpg/460px-Wow2_filtered.jpg
- (c) Michael Rosenberg, some rights reserved (CC BY-NC), http://farm4.static.flickr.com/3473/3702368790_4421be340f.jpg
- (c) Wikipedia, some rights reserved (CC BY-SA), http://en.wikipedia.org/wiki/Circus_cyaneus
- (c) Muséum national d'Histoire naturelle. Service du Patrimoine naturel, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/29862174
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31386559
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31386561
- (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28920099
- (c) The Regents of the University of Michigan and its licensors, some rights reserved (CC BY-NC-SA), http://eol.org/data_objects/31386560
- (c) NatureServe, some rights reserved (CC BY-NC), http://eol.org/data_objects/28920102
