[order] ACCIPITRIFORMES | [family] Accipitridae | [latin] Buteo galapagoensis | [authority] Gould, 1837 | [UK] Galapagos Hawk | [FR] Buse des Galapagos | [DE] Galapagosbussard | [ES] Busardo de galapagos | [NL] Galapagosbuizerd
Members of the genus Buteo are broad-winged, broad-tailed hawks, Well adapted for soaring. The bill, legs and talons are of average proportions. There is much colour variation both within the species, and, by way of phases, within individual species. In all cases the young are quite different from adults in that they are all well camouflaged with an overall brown appearance with varying amounts of striping below and paler mottling above.
The 25 species are spread worldwide with the exception of Australasia and much of the Indian sub-continent.
The adult Galapagos Hawk is generally a sooty brownish black colour; the crown being slightly blacker than the back. The feathers of the mantle are partially edged with paler brown, grey, or buff, with their white bases showing to some extent. The tail coverts are also barred with white. The tail itself is silvery grey above, with about ten narrow black bars; below it is quite pale. The wing feathers are paler on inner webs, barred with white. Below it has indistinct rufous edges to the feathers of the flanks and lower abdomen. The under-tail coverts are barred with white. Under-wing coverts are black, contrasting with the pale bases of the wing quills. The eyes are brown, the bill greyish black, paler at its base; the cere, legs and feet are yellow. The male is a good bit smaller than the female. Immatures are blackish brown above, mottled with buff and white. The tail is buffy white with about twelve narrow wavy black bars. Below, including wing lining, is rich buff, paler on the throat, with numerous black-brown oval or wedge- shaped spots. A black area extends back from corners of mouth. The eyes are light grey-brown, and the bill black, blue-grey at its base. The cere is grey-green, the feet pale yellow-green. When the immature plumage becomes badly worn, the pale areas become almost white.
South America : Galapagos Islands. Islands of the Galapagos. The population is difficult to measure except in terms of breeding territories, of which 130 were estimated in the early 1970s. Following a serious population decline, it is now extinct on five islands, greatly reduced on Santa Cruz (2 territories), and present on Santiago (c.50), Espanola (10), Isabela (c.25), Fernandina (10), Pinta (6), Marchena (5), Pinzon (5)
and Santa Fe (17)
It is found in all habitats, from shoreline to bare lava-fields, open, rocky, scrub country, deciduous forests and mountain peaks. It feeds on a wide variety of sea and landbirds, rats, lizards, iguanas, invertebrates and carrion. It breeds throughout the year. It nests on a stick platform on a prominent lava outflow, rocky outcrop or in a small tree.
A nest is used for many years, and becomes quite large, perhaps four feet in diameter. It is made of sticks, lined with grass, clumps of leaves, bark, or whatever other soft material may be available, and is placed in a low tree, on a ledge of lava or even on the ground. The sticks are usually twelve to eighteen inches long and a quarter to three-eighths of an inch in diameter. At the peak of the display and egg-laying season the pair are together most of the time and remain close to the nest site. Their legs are often dangled in flight, either when the pair make aerial passes at one another, or as one of them drops slowly to a perch. Mating takes place several times a day, with no preliminary display, on any perch, often at some distance from the nest. Though very approachable, they will abandon a nest that has been disturbed by humans. One or two green-white, unmarked, eggs are laid but usually only one young is reared. Fresh green twigs are brought to maintain the nest, sometimes inadvertently covering the eggs, but not hindering incubation. Laying times vary, and there may be no regular season. The eggs are incubation for 5 to 6 weeks, the chick fledges after another 2 months. The species is polyandrous with females having up to 7 males involved in copulation. These co-parents also help incubate the eggs, defend the nest and feed the young or incubating parent. However, not all females have more mates, but the mortality rate of the chicks is significantly lower in the polyandrous groups.
This bird subsists almost entirely on giant centipedes, locusts, small lava lizards, snakes and rodents. It takes young marine iguanas rather commonly. It also catches young land iguanas, hatchling tortoises and probably also hatchling sea turtles. It has been seen to remain near nesting Fork-tailed Gulls and probably takes young and perhaps eggs of these and other birds, as well as poultry. Carrion is taken even when very putrid, except seals. It has also been seen to pick bits of flesh and fat from staked out hides.
copyright: Peter van Dam
This species is listed as Vulnerable because it has a small population. Trends are not clear, but are assumed to be stable. If threats, notably persecution, were shown to be causing a decline, this species would warrant uplisting to Endangered.
The most probable cause of the species’s historical decline is persecution by humans, which still continues on Santa Cruz and south Isabela. The largest island, Isabela, may support a comparatively small population owing to competition for food with introduced feral cats and other predators. Similar scenarios may have been partly responsible for the local extinctions.