The Galápagos hawk (''Buteo galapagoensis'') is a large hawk
endemic
Endemism is the state of a species being found in a single defined geographic location, such as an island, state, nation, country or other defined zone; organisms that are indigenous to a place are not endemic to it if they are also found else ...
to most of the
Galápagos Islands
The Galápagos Islands ( Spanish: , , ) are an archipelago of volcanic islands. They are distributed on each side of the equator in the Pacific Ocean, surrounding the centre of the Western Hemisphere, and are part of the Republic of Ecuad ...
.
Description
The Galapágos hawk is similar in size to the
red-tailed hawk (''Buteo jamaicensis'') and the
Swainson's hawk (''Buteo swainsoni'') of
North America
North America is a continent in the Northern Hemisphere and almost entirely within the Western Hemisphere. It is bordered to the north by the Arctic Ocean, to the east by the Atlantic Ocean, to the southeast by South America and th ...
, 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
The Americas, which are sometimes collectively called America, are a landmass comprising the totality of North America, North and South America. The Americas make up most of the land in Earth's Western Hemisphere and comprise the New World. ...
, behind only the
ferruginous hawk. The Galapágos hawk can range from in length from beak to tail with a wingspan of .
[Del Hoyo, J., & Elliot, A. I SARGATAL, J. eds. 1994. ''Handbook of the birds of the World. Vol. 2. New World Vultures to Guineafowl''. Lynx Edicions, Barcelona.] 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 . Largest known are the hawks on
Española Island
Española Island (Spanish: ''Isla Española'') is part of the Galápagos Islands. The English named it ''Hood Island'' after Viscount Samuel Hood. It is located in the extreme southeast of the archipelago and is considered, along with Sant ...
, which are amongst the largest ''Buteo'' known anywhere, with males averaging and females averaging .
['' CRC Handbook of Avian Body Masses, 2nd Edition'' by John B. Dunning Jr. (Editor). CRC Press (2008), .] 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.
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 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.
The Galapágos hawk has broad wings and a broad tail. It is an
apex predator and possesses excellent vision. Their young appear different from adults because they are darker and have camouflage which aids them in remaining protected from potential predators until they are fully grown.
Habitat and diet
This hawk lives mainly on insects such as
locusts
Locusts (derived from the Vulgar Latin ''locusta'', meaning grasshopper) are various species of short-horned grasshoppers in the family Acrididae that have a swarming phase. These insects are usually solitary, but under certain circumstanc ...
and giant
centipedes
Centipedes (from New Latin , "hundred", and Latin , "foot") are predatory arthropods belonging to the class Chilopoda (Ancient Greek , ''kheilos'', lip, and New Latin suffix , "foot", describing the forcipules) of the subphylum Myriapoda, an a ...
, as well as small lava
lizards
Lizards are a widespread group of squamate reptiles, with over 7,000 species, ranging across all continents except Antarctica, as well as most oceanic island chains. The group is paraphyletic since it excludes the snakes and Amphisbaenia altho ...
,
snakes
Snakes are elongated, limbless, carnivorous reptiles of the suborder Serpentes . Like all other squamates, snakes are ectothermic, amniote vertebrates covered in overlapping scales. Many species of snakes have skulls with several more j ...
, and
rodents
Rodents (from Latin , 'to gnaw') are mammals of the order Rodentia (), which are characterized by a single pair of continuously growing incisors in each of the upper and lower jaws. About 40% of all mammal species are rodents. They are na ...
. It is not uncommon for it to take
marine
Marine is an adjective meaning of or pertaining to the sea or ocean.
Marine or marines may refer to:
Ocean
* Maritime (disambiguation)
* Marine art
* Marine biology
* Marine debris
* Marine habitats
* Marine life
* Marine pollution
Military ...
and
land iguanas,
Galápagos sea lion pups, and
sea turtle
Sea turtles (superfamily Chelonioidea), sometimes called marine turtles, are reptiles of the order Testudines and of the suborder Cryptodira. The seven existing species of sea turtles are the flatback, green, hawksbill, leatherback, loggerhe ...
and
tortoise
Tortoises () are reptiles of the family Testudinidae of the order Testudines (Latin: ''tortoise''). Like other turtles, tortoises have a shell to protect from predation and other threats. The shell in tortoises is generally hard, and like oth ...
hatchlings. This predator has also been spotted near nesting areas of
swallow-tailed gulls, where it steals eggs as well as young. Even extremely rancid carrion is picked apart by their sharp, forceful beaks. Their feet and talons are also strong like those of the closely related
variable hawk
The variable hawk (''Geranoaetus polyosoma'') is a polymorphic species of bird of prey in the family Accipitridae.
It is widespread and often common in open habitats in western and southern South America, including the Falkland Islands. Its ta ...
and
white-tailed hawk.
Hunting in groups of two or three, the hawks soar at a height of in the sky. When one of the birds spots prey or a rotting carcass, they signal to the other members. The dominant hawk of the group feeds from the prey until it is satisfied, as the other hawks in the family group submissively wait their turn to feed. It prefers to perch on a lava outcrop or high branch when hunting, yet it also spends some of its time on the ground.
Fearless of man, the young especially being quite curious, often wandering around human camps and scavenging for scraps of food. In 1845,
Charles Darwin
Charles Robert Darwin ( ; 12 February 1809 – 19 April 1882) was an English naturalist, geologist, and biologist, widely known for his contributions to evolutionary biology. His proposition that all species of life have descended ...
wrote:
"A gun is here almost superfluous; for with the muzzle I pushed a hawk out of the branch of a tree..."
Behavior and breeding
Because the seasons of the island are unchanging due to the close proximity of the
equator
The equator is a circle of latitude, about in circumference, that divides Earth into the Northern and Southern hemispheres. It is an imaginary line located at 0 degrees latitude, halfway between the North and South poles. The term can also ...
, there is no regular mating season. Mating takes place 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. While males tend to be
monogamous
Monogamy ( ) is a form of dyadic relationship in which an individual has only one partner during their lifetime. Alternately, only one partner at any one time ( serial monogamy) — as compared to the various forms of non-monogamy (e.g., pol ...
, the females will mate with up to seven different males during the mating season. Throughout the entire nesting period, the female and her males take turns protecting the nest and incubating the eggs, even participating in the feeding.
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. The mating pair is together with the majority of the time at the prime of the egg-laying season and usually stays close to the nesting site. The nest is maintained constantly with fresh, green twigs. Normally one to three eggs are laid, green-white in color, but only one young is reared. 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. Although these birds are generally fearless, they will abandon their nest if it has been tampered with by humans.
Voice
The call of the Galapágos hawk is a series of short screams similar to the call of the
red-shouldered hawk that have been described as a “''keer, keeu'',” or an inflected “''kwee''”. Especially noisy during mating season, their call softens to a “''kilp, kilp, kilp''”.
Status
Although the exact number of these birds is unknown, there are believed to be only around 150 mating pairs in existence today. This statistic has improved slightly from past years, but it is far from the abundance they were found in on all the islands of Galápagos when they were discovered. Due to human disturbance to their natural habitat, a dwindling food supply because of new predators introduced to the islands, and persecution by humans, they are now extinct on the islands of
Baltra
Baltra Island (Spanish: ''Isla Baltra''), is a small island of the Galápagos Islands. Also known as South Seymour (named after Lord Hugh Seymour), Baltra is a small flat island located near the center of the Galápagos. It was created by geolo ...
,
Daphne Major,
Floreana
Floreana Island (Spanish: ''Isla Floreana'') is an island of the Galápagos Islands. It was named after Juan José Flores, the first president of Ecuador, during whose administration the government of Ecuador took possession of the archipelago. ...
,
San Cristóbal, and
North Seymour.
Evolution
The study of mtDNA haplotypes (Bollmer et al. 2005) of the Galapágos hawk and its closest relative,
Swainson's hawk, indicates that the former's ancestors colonized the islands approximately 300,000 years ago, making the birds the most recent native species arrival known. By contrast,
Darwin's finches
Darwin's finches (also known as the Galápagos finches) are a group of about 18 species of passerine birds. They are well known for their remarkable diversity in beak form and function. They are often classified as the subfamily Geospizinae or ...
are estimated to have arrived some 2–3 million years ago.
References
* 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
.
* 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.
External links
BirdLife Species Factsheet.
ARKive:
images and movies of the Galapagos hawk (''Buteo galapagoensis'')
AnimalsandEarth:
photos of the Galapagos hawk (''Buteo galapagoensis'')
{{Taxonbar, from=Q840141
Galapagos hawk
Endemic birds of the Galápagos Islands
Galapagos hawk
Galapagos hawk
Apex predators