Sunday, March 18, 2012

>Accipiter gentilis (Northern Goshawk)

Northern Goshawk

Northern Goshawk
Conservation status
Scientific classification
(or Accipitriformes, q.v.)
Species:A. gentilis
Binomial name
Accipiter gentilis
(Linnaeus, 1758)
Accipiter gentilis albidus
Accipiter gentilis apache
Accipiter gentilis arrigonii
Accipiter gentilis atricapillus
Accipiter gentilis buteoides
Accipiter gentilis fujiyamae
Accipiter gentilis gentilis
Accipiter gentilis laingi
Accipiter gentilis marginatus
Accipiter gentilis schvedowi
Range map
yellow: breeding
green: year-round
blue: wintering.
The Northern Goshawk /ˈɡɒs.hɔːk/ (Old Englishgōsheafoc, "goose-hawk"), Accipiter gentilis, is a medium-large bird of prey in the family Accipitridae, which also includes other diurnal raptors, such as eaglesbuzzards and harriers.
It is a widespread species that inhabits the temperate parts of the northern hemisphere. In Europe and North America, where there is only one goshawk, it is often referred to (officially and unofficially, respectively) as simply the "Goshawk". It is mainly resident, but birds from colder regions migrate south for the winter. In North America, migratory goshawks are often seen migrating south along mountain ridge tops in September and October.
This species was first described by Linnaeus in his Systema naturae in 1758 under its current scientific name.
The Northern Goshawk appears on the flag of the Azores. The archipelago of the AzoresPortugal, takes its name from the Portuguese language word for goshawk, (açor), because the explorers who discovered the archipelago thought the birds of prey they saw there were goshawks; later it was found that these birds were kites or Common Buzzards (Buteo buteo rothschildi).


Juvenile (left) and adult by Louis Agassiz Fuertes

Juvenile in flight
The Northern Goshawk is the largest member of the genus Accipiter. It is a raptor with short, broad wings and a long tail, both adaptations to manoeuvring through trees in the forests it lives and nests in. Across most of the species's range, it is blue-grey above and barred grey or white below, but Asian subspecies in particular range from nearly white overall to nearly black above. Juveniles and adults have a barred tail, with dark brown or black barring. Adults always have a white eye stripe. In North America, juveniles have pale-yellow eyes, and adults develop dark red eyes usually after their second year, although nutrition and genetics may affect eye color as well. In Europe and Asia, juveniles also have pale-yellow eyes, however adults develop orange-colored eyes. The Northern Goshawk, like all accipiters, exhibits sexual dimorphism, where females are significantly larger than males. Males, being able 10–25% smaller in body are size, are 46–57 cm (18–22 in) long with a 89–105 cm (35–41 in) wingspan. The female is much larger, 58–64 cm (23–25 in) long with a 108–127 cm (43–50 in) wingspan. Males of the smaller races can weigh as little as 515 grams (18.2 oz), whereas females of the larger races can weigh as much as 2.2 kg (4.9 lb).Females are often 30–60% heavier than their mates. The juvenile is brown above and barred brown below. The flight is a characteristic "flap flap, glide", but is sometimes seen soaring in migration, and is capable of considerable, sustained, horizontal speed in pursuit of prey with speeds of 38 mph (61 km/h) reported.Goshawks are sometimes confused with gyrfalconsespecially when observed in high speed pursuit, with their wingtips drawn backward in a falcon-like profile.
In Eurasia, the male is sometimes confused with a female Sparrowhawk, but is larger, much bulkier and has relatively longer wings. In North America, juveniles are sometimes confused with the smaller Cooper's Hawk, however the juvenile goshawk displays a heavier, vertical streaking pattern on their chest and abdomen and sometimes appears to have a shorter tail due to its much larger and broader body. Although there appears to be a size overlap between small male goshawks and large female Cooper's Hawks, morphometric measurements (wing and tail length) of both species demonstrate no such overlap, although weight overlap can occur due to variation in seasonal condition and food intake at time of weighing. In North America, the Sharp-shinned Hawkis markedly smaller.

Food and hunting

This species hunts birds and mammals in a variety of woodland habitats, often utilizing a combination of speed and obstructing cover to ambush birds and mammals. Goshawks are often seen flying along adjoining habitat types, such as the edge of a forest and meadow; flying low and fast hoping to surprise unsuspecting prey. They are usually opportunistic predators, as are mostbirds of prey. The most important prey species are small mammals and birds found in forest habitats, especially grouseAmerican Crowsnowshoe hare, and red squirrel in North America. Compared to many smaller Accipiter species, Northern Goshawks are less specialized as predators of birds, with up to 69% of their diet comprised by either birds or mammals depending on location. Prey species may be quite diverse, including pigeons and dovespheasants,partridgesgrousegulls, assorted waderswoodpeckerscorvidswaterfowl (mostly tree-nesting varieties such as the Aythya genus ) and various passerines depending on the region. Mammal prey may include rabbitsharestree squirrelground squirrelchipmunksratsvolesmice,weasels and shrews. Prey is often smaller than the hunting hawk, with an average prey mass of 275 g (9.7 oz) in one study of nesting birds in Minnesota. However, Northern Goshawks will also occasionally kill much larger animals, up to the size of raccoonsfoxes and large hares which can be more than twice their own weight. The Goshawk is likely a significant predator of otherraptors, known prey including honey-buzzardsowls, smaller Accipiters and the American Kestrel.


In the spring breeding season, Northern Goshawks perform a spectacular "undulating flight display", and this is one of the best times to see this secretive forest bird. At this time, the surprisingly gull-like call of this bird is sometimes heard. Adults defend their territories fiercely from intruders, including passing humans. It is presumed that their unusually aggressive nest defense is an adaptation to tree-climbing bears species, such as the black bear in North America. Other raptors are also attacked at nest sites, and often cede territory to, or are themselves killed by the aggressive Goshawk. The Northern Goshawk is considered a secretive raptor, and is rarely observed even in areas where nesting sites are common.


Adults return to their nesting territories by March or April and begin laying eggs in April or May. Territories often encompass a variety of habitats, however the immediate nest area is often found in a mature or old-growth forest. The clutch size is usually 2 to 4, but anywhere from 1 to 5 eggs may be laid. The eggs average 59 × 45 mm (2.3 × 1.8 in) and weigh about 60 g (2.1 oz). The incubation period can range from 28 to 38 days. The young leave the nest after about 35 days and start trying to fly another 10 days later. The young may remain in their parents' territory for up to a year of age.


In the United Kingdom and Ireland, the Northern Goshawk was extirpated in the 19th century because of specimen collectors and persecution by gamekeepers, but in recent years it has come back by immigration from Europe, escaped falconry birds, and deliberate releases. The Goshawk is now found in considerable numbers in Kielder ForestNorthumberland, which is the largest forest in Britain. The main threat to Northern Goshawks internationally today is the clearing of forest habitat on which both they and their prey depend, and in Britain illegal shooting and poisoning for game preservation when young dispersing move into farming areas.
In North America, several non-governmental conservation organizations petitioned the Department of Interior, United States Fish & Wildlife Service (1991 & 1997) to list the Goshawk as "threatened" or "endangered" under the authority of the Endangered Species Act. Both petitions argued for listing primarily on the basis of historic and ongoing nesting habitat loss, specifically the loss of old-growth and mature forest stands throughout the goshawk's known range. In both petitions, the U.S. Fish & Wildlife Service concluded that listing was not warranted, but state and federal natural resource agencies responded during the petition process with standardized and long-term goshawk inventory and monitoring efforts, especially throughout U.S. Forest Service lands in the Western U.S. The United States Forest Service (US Dept of Agriculture) has listed the goshawk as a "sensitive species", while it also benefits from various protection at the state level. In North America, the goshawk is federally protected under the Migratory Bird Treaty Act of 1918 by an amendment incorporating native birds of prey into the Act in 1972. The Northern Goshawk is also listed in Appendix II of the Convention on International Trade in Endangered Species (CITES) .

In falconry

A falconer's bird in Scotland
The name "goshawk" is a traditional name from Anglo-Saxon gōshafoc, literally "goose hawk".The name implies prowess against larger quarry such as geese, but were also flown against crane species and other large waterbirds. The name "goose hawk" is somewhat of a misnomer however, as the traditional quarry for goshawks in ancient and contemporary falconry has been rabbits, pheasants, partridge, and medium sized waterfowl. A notable exception is in records of traditional Japanese falconry, where goshawks were used more regularly on goose and crane species. In ancient European falconry literature, goshawks were often referred to as a yeoman's bird or the "cook's bird" due to their utility as a hunting partner as opposed to the peregrine falcon, also a prized falconry bird, but more associated with nobleman and less adapted to a variety of hunting techniques and prey types found in wooded areas. The Northern Goshawk has remained equal to the peregrine falcon in its stature and popularity in modern falconry.
Goshawk hunting flights in falconry typically begin from the falconer's gloved hand, where the fleeing bird or rabbit is pursued in a horizontal chase. The goshawk's flight in pursuit of prey is characterized by an intense burst of speed often followed by a binding maneuver, where the goshawk seizes its prey in an inverted position below its winged quarry. The goshawk, like other accipiters, shows a marked willingness to follow prey into thick vegetation, even pursuing prey on foot through brush.

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