The Galápagos hawk (Buteo galapagoensis) is a large hawk endemic to most of the Galápagos Islands.

Description

upright|thumb|left|Juvenile

The Galapágos hawk is similar in size to the red-tailed hawk (Buteo jamaicensis) and the Swainson's hawk (Buteo swainsoni) of North America, but the size is variable across the islands as is recorded for many animals native to the Galapágos. They appear to be somewhat more heavily built than those well-known mainland species, and going on average weights, this species is the second heaviest Buteo in the Americas, behind only the ferruginous hawk. The Galapágos hawk can range from in length from beak to tail with a wingspan of . The smallest hawk sizes recorded are on Marchena Island, where males average and females average . Intermediate in size are the hawks of Santiago Island, on which males weigh an average of while females average . The largest known are the hawks on Española Island, which are amongst the largest Buteo known anywhere, with males averaging and females averaging . The adult hawk has various coloring within the species.

The adult Galapagos hawk is generally a sooty brownish-black color; the crown being slightly blacker than the back. Its feathers of the mantle are partially edged with paler brown, grey, or buff, with their white bases showing to some extent. Their 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 beak greyish black, paler at its base which is known as the 'cere', legs, and feet are yellow. The male hawk is smaller than the female hawk, as with many birds of prey.

thumb|right|Galapagos hawk in flight.

The young hawks however appear quite different from the adults in that they are well camouflaged with an overall brown appearance with varying amounts of striping below and paler mottling above. Their eyes are light grey-brown, and the beak is 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. It is not uncommon for it to take marine iguanas (Amblyrhynchus cristatus). Most of the marine iguana prey are mainly hatchlings and juveniles but occasionally adults, especially nesting females. The Galapagos hawk can kill relatively large individuals, which can weigh at least equal to the hawk's own weight or even heavier. Hatchlings of tortoise, sea turtle, and land iguanas are additionally taken, as well as young of Galápagos sea lions, feral pigs, and goats. Arboreal prey include Galapagos Doves (Zenaida galapagoensis), Galapagos Mockingbirds (Mimus parvulus), and Darwin's finches (Geospiza spp. & Camarhynchus spp.), from their egg to full-grown adults. Regular predation on blue-footed booby (Sula nebouxii) nestlings, which can weigh around 1280g, has been reported. Aside from live prey, carrions are additionally taken, from dead seals to fish scraps.

Fearless of man, the young especially being quite curious, often wandering around human camps and scavenging for scraps of food. In 1845, Charles Darwin wrote:

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A gun is here almost superfluous; for with the muzzle I pushed a hawk out of the branch of a tree...

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Behavior and breeding

thumb|A possible breeding pair of adults on [[Santa Fe Island.]]

Because the seasons of the island are unchanging due to the close proximity of the equator, there is no regular mating season. Mating occurs a few times a day on a nearby perch or in flight. It begins when males make fake attacks on the female from behind by dive-bombing her, and then the male follows the female as she descends to the trees below. Nests are built low in trees, on lava ledges, or even on the ground at times. Used for many years and nesting periods, they become quite large, sometimes even four feet in diameter. Stick structures are lined with grass, bark, clumps of leaves, or other available soft materials. Young hawks leave the nest around 50–60 days after hatching. Juvenile hawks will not enter the territorial breeding areas until they reach the age of three, becoming sexually mature.

References

Further reading

  • Bollmer, Jennifer L.; Kimball, Rebecca T.; Whiteman, Noah Kerness; Sarasola, José Hernán & Parker, Patricia G. (2005). Phylogeography of the Galápagos hawk (Buteo galapagoensis): A recent arrival to the Galápagos Islands. Molecular Phylogenetics and Evolution 39(1): 237–247. (HTML abstract)
  • Channing, Keith (2008). Galapagos Hawk - Buteo galapagoensis. The Hawk Conservancy Trust. 5 March 2008.
  • Licon, Daniel. "Buteo galapagoensis: Galapagos Hawk". University of Michigan Museum of Zoology Animal Diversity Web. 2008. 5 Mar 2008 <http://animaldiversity.ummz.umich.edu/site/accounts/information/Buteo_galapagoensis.html>.
  • Bollmer, Jennifer L., et al. (2005). Population Genetics of the Galapagos Hawk (Buteo galapagoensis): Genetic Monomorphism Within Isolated Populations. The Auk 122(4): 1210–1214.
  • Delay, Linda S., et al. (1996). Paternal Care in the Cooperatively Polyandrous Galapagos Hawk. The Condor 98: 300–306.
  • BirdLife Species Factsheet.
  • ARKive: images and movies of the Galapagos hawk (Buteo galapagoensis)
  • AnimalsandEarth: photos of the Galapagos hawk (Buteo galapagoensis)