Gabar goshawk

Description

The gabar goshawk is polymorphic and occurs in two distinct forms which fluctuate in relative abundance across the geographic range of the species. The more frequent, paler form has mostly grey upperparts with a conspicuous, white rump and white and grey barring on the chest, thighs and underwings, and a dark grey, barred tail. In contrast, the less frequent form, which accounts on average for approximately 25 percent of the overall population, is almost completely black. In both forms of adult the eyes are dark, and the long legs and the cere are red. The cere and the legs are yellow in immatures and the plumage is generally browner, with the pale birds having untidy barring on the chest than the adult. The females are significantly larger than the males, the male's weigh 90 - 173g and the females 167 - 240g The body length is 28–36 cm and the wingspan 63 cm.

Distribution and subspecies

The gabar goshawk is found in sub-Saharan Africa, extending to Arabian Peninsula. The following subspecies are currently recognised:

Habitat

The gabar goshawk occurs in open woodland, especially dry Acacia savanna and broad-leaved woodland, with miombo Brachystegia, cluster-leaf Terminalia and Mopane Colosphermum mopane. In the more arid regions of southern Africa such as the Karoo and Namib Desert, it is generally restricted to tree-lined watercourses, but it may also move into cities and towns.

Biology

The gabar goshawk is usually considered to be sedentary, but immature birds are somewhat nomadic and some small migratory movements have been recorded in parts of its range. It is most frequently observed alone but pairs are also common, particularly during the breeding season when the male is often observed pursuing the female through trees, or calling from his perch. The small platform nest is typically constructed using thin twigs and positioned in a vertical fork in the crown of a thorny tree, such as an acacia. One notable aspect of their nest construction is that the birds collect spider webs including the live spiders, the spiders spin new webs which may help camouflage the nest and it is also thought that the spiders may consume arthropods that would parasitize the chicks.

The eggs are laid from July–December, peaking in September to November. The normal clutch is two eggs but up to four may be laid and these are mainly incubated by the female for about 33–38 days. Once hatched the chicks are brooded by the female for the first 19–21 days of their lives, while the male brings her food to feed to them. They leave the nest at about 35–36 days old, becoming fully independent around one month month later.

Small birds are the major part of the gabar goshwak’s diet, with small mammals, reptiles and insects also taken on occasion. The prey is typically flushed from trees and caught following a persistent and energetic pursuit. The gabar goshawk sometimes hunts from the perch, swooping down to catch prey off the ground or in flight. They have also been recorded attacking the nests of colonial birds such as weavers by clawing its way destructively through the nest top to snatch the chicks from the nest.

Known predators of the gabar goshawk include Tawny Eagle, Wahlberg's Eagle and Ayres's hawk-eagle.