Sparviere eurasiatico

Identificazione

The Eurasian sparrowhawk is a small bird of prey with short, broad wings and a long tail, both adaptations to manoeuvring through trees. Females can be up to 25% larger than males and weigh up to twice as much. Marked size difference in this direction is unusual in higher vertebrates but typical in birds of prey, and most marked in birds of prey which hunt other birds.<p>The adult male is 29–34 cm (11–13 in) long, with a wingspan of 59–64 cm (23–25 in) and a mass of 110–196 g (3.9–6.9 oz). He has slate-grey upperparts (sometimes tending to bluish), with finely red-barred underparts, which can look plain orange from a distance; his irides are orange-yellow or orange-red. The female is much larger at 35–41 cm (14–16 in) long, with a wingspan of 67–80 cm (26–31 in), and a mass of 185–342 g (6.5–12.1 oz). She has dark brown or greyish-brown upperparts, and brown-barred underparts, and bright yellow to orange irides. The juvenile is warm brown above, with rusty fringes to the upperparts; and coarsely barred or spotted brown below, with pale yellow eyes; its throat has dark streaks and lacks a mesial (midline) stripe.<p>The Eurasian sparrowhawk's pale underparts and darker upperparts are an example of countershading, which helps to break up the bird's outline. Countershading is exhibited by birds of prey which hunt birds and other fast-moving animals. The horizontal barring seen on adult Eurasian sparrowhawks is typical of woodland-dwelling predatory birds, while the adult male's bluish colour is also seen in other bird-eating raptors, including the peregrine falcon, the merlin and other Accipiters.<p>A study, using stuffed bird models, found that small birds are less likely to approach common cuckoos (a brood parasite) which have barred underparts like the Eurasian sparrowhawk. Eurasian reed warblers were found to be more aggressive to cuckoos which looked less hawk-like, meaning that the resemblance to the hawk (mimicry) helps the cuckoo to access the nests of potential hosts.<p>The Eurasian sparrowhawk's small bill is used for plucking feathers and pulling prey apart, rather than killing or cutting. Its long legs and toes are an adaptation for catching and eating birds. The outer toe is "fairly long and slender"; the inner toe and back toe are relatively short and thick. The middle toe is very long and can be used to grasp objects, while a protuberance on the underside of the toe means that the digit can be closed without leaving a gap, which helps with gripping.<p>The flight is a characteristic "flap-flap-glide", with the glide creating an undulating pattern. This species is similar in size to the Levant sparrowhawk, but larger than the shikra (the calls are however different); the male is only slightly larger than the merlin. Because of the overlap in sizes, the female can be confused with the similarly sized male Eurasian Goshawk, but lacks the bulk of that species. Eurasian sparrowhawks are smaller, more slender and have shorter wings, a square-ended tail and fly with faster wingbeats. A confusion species in China is the besra, although A. n. melaschistos is considerably larger.<p>In Great Britain, Eurasian sparrowhawks living further north are bigger than their more southerly counterparts, with wing length (the most reliable indicator of body size) increasing by an average of 0.86 mm (0.034 in) in males, and 0.75 mm (0.030 in) in females, for each degree further north.

Tassonomia

Within the family Accipitridae, the Eurasian sparrowhawk is a member of the large genus Accipiter, which consists of small to medium-sized woodland hawks. Most of the Old World members of the genus are called sparrowhawks or goshawks. The species' name dates back to the Middle English word sperhauk and Old English spearhafoc, a hawk which hunts sparrows. The Old Norse name for the Eurasian sparrowhawk, sparrhaukr, was thought to have been coined by Vikings who encountered falconry in England. English folk names for the Eurasian sparrowhawk include blue hawk, referring to the adult male's colouration, as well as hedge hawk, spar hawk, spur hawk and stone falcon.<p>The Eurasian sparrowhawk was described by Carl Linnaeus in his 1758 landmark 10th edition of Systema Naturae, as Falco nisus, but moved to its present genus by French zoologist Mathurin Jacques Brisson in 1760. The current scientific name is derived from the Latin accipiter, meaning 'hawk' and nisus, the sparrowhawk. According to Greek mythology, Nisus, the king of Megara, was turned into a sparrowhawk after his daughter, Scylla, cut off his purple lock of hair to present to her lover (and Nisus' enemy), Minos.<p>The Eurasian sparrowhawk forms a superspecies with the rufous-chested sparrowhawk of eastern and southern Africa, and possibly the Madagascar sparrowhawk. Geographic variation is clinal, with birds becoming larger and paler in the eastern part of the range compared to the western part. Within the species itself, six subspecies are generally recognised:

Nome scientifico

Accipiter nisus

Autorità

(Linnaeus, 1758)

Ordine

Accipitriformi

Famiglia

Accipitridae

Genere

Accipiter

Areale e habitat

A widespread species throughout the temperate and subtropical parts of the Old World, the Eurasian sparrowhawk is resident or breeds in an estimated global range of 23,600,000 km2 (9,100,000 sq mi) and had an estimated population of 1.5 million birds in 2009. Although global population trends have not been analysed, numbers seem to be stable, so it has been classified as being of least concern by IUCN. The race granti, with 100 pairs resident on Madeira and 200 pairs on the Canary Islands, is threatened by loss of habitat, egg-collecting and illegal hunting, and is listed on Annex I of the European Commission Birds Directive. It is one of the most common birds of prey in Europe, along with the common kestrel and common buzzard. The Norwegian and Albanian populations are declining and, in many parts of Europe, Eurasian sparrowhawks are still shot. However, this low-level persecution has not affected the populations badly. In the UK, the population increased by 108% between 1970 and 2005, but saw a 1% decline over 1994–2006. In Ireland it is the most common bird of prey, breeding even near the city centre of Dublin, where it frequents parks and large gardens.<p>This species is prevalent in most woodland types in its range, and also in more open country with scattered trees. Eurasian sparrowhawks prefer to hunt the edges of wooded areas, but migrant birds can be seen in any habitat. The increased proportion of medium-aged stands of trees created by modern forestry techniques have benefited Accipiter nisus, according to a Norwegian study. Unlike its larger relative the Eurasian Goshawk, it can be seen in gardens and in urban areas and will even breed in city parks if they have a certain density of tall trees.<p>Eurasian sparrowhawks from colder regions of northern Europe and Asia migrate south for the winter, some to north Africa (some as far as equatorial east Africa) and India; members of the southern populations are resident or disperse. Juveniles begin their migration earlier than adults and juvenile females move before juvenile males. Analysis of ringing data collected at Heligoland, Germany, found that males move further and more often than females; of migrating birds ringed at Kaliningrad, Russia, the average distance moved before recovery (when the ring is read and the bird's whereabouts reported subsequently) was 1,328 km (825 mi) for males and 927 km (576 mi) for females.<p>A study of Eurasian sparrowhawks in southern Scotland found that ringed birds which had been raised on "high grade" territories were recovered in greater proportion than birds which came from "low grade" territories. This suggested that the high grade territories produced young which survived better. The recovery rate also declined with increased elevation of the ground. After the post-fledging period, female birds dispersed greater distances than did males.

Areale riproduttivo

PAL : widespread

Areale non riproduttivo

OR, ne AF

Migrazione

Complete migrants

Conservazione

Tendenza della popolazione

stable