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. When females are larger than males, it is known as reverse sexual dimorphism; this is unusual in higher vertebrates but typical in birds of prey, and most marked in birds of prey which hunt birds. 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. 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.
Habitat and Distribution
The Eurasian Sparrowhawk is a widespread species throughout the temperate and subtropical parts of the Old World. It is one of the most common birds of prey in Europe, along with the Common Kestrel and Common Buzzard. This species is common in most woodland types in its range and also in more open country with scattered trees. Eurasian Sparrowhawks prefer to hunt woodland edges, 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 the species, according to a Norwegian study. Unlike its larger relative the Northern Goshawk, it can be seen in gardens and in urban areas and will even breed in city parks. 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.
The Eurasian Sparrowhawk is a major predator of smaller woodland birds, though only 10% of its hunting attacks are successful. It hunts by surprise attack, using hedges, tree-belts, copses, orchards and other cover near woodland areas; its choice of habitat is dictated by these requirements. It also makes use of gardens in built-up areas, taking advantage of the prey found there. It waits, hidden, for birds to come near, then breaks cover and flies out fast and low. A chase may follow, with the hawk even flipping upside-down to grab the victim from below or following it on foot through vegetation. It can `stoop` onto prey from a great height.
The Eurasian Sparrowhawk breeds in well-grown, extensive areas of woodland, often coniferous or mixed, preferring forest with a structure neither too dense nor too open, to allow a choice of flight paths. The nest can be located in the fork of a tree, often near the trunk and where two or three branches begin, on a horizontal branch in the lower canopy, or near the top of a tall shrub. If available, conifers are preferred.The structure, made of loose twigs up to 60 cm (2.0 ft) long, has an average diameter of 60 cm (24 in). When the eggs are laid, a lining of fine twigs or bark chippings is added. The eggs are pale blue with brown spots and each measure 35-46 x 28-35 mm (1.4-1.8 x 1.1-1.4 inches), and weigh about 22.5 g (0.8 oz) of which 8% is shell in a healthy egg. Usually a clutch of four or five eggs is laid. The eggs are generally laid in the morning with an interval of 2-3 days between each egg. If a clutch is lost, up to two further eggs may be laid that are smaller than the earlier eggs.