Swallow-tailed gull | |
---|---|
On the Galápagos Islands | |
Scientific classification | |
Domain: | Eukaryota |
Kingdom: | Animalia |
Phylum: | Chordata |
Class: | Aves |
Order: | Charadriiformes |
Family: | Laridae |
Genus: | Creagrus Bonaparte, 1854 |
Species: | C. furcatus |
Binomial name | |
Creagrus furcatus (Neboux, 1842) | |
The swallow-tailed gull (Creagrus furcatus) is an equatorial seabird in the gull family, Laridae. It is the only species in the genus Creagrus, which derives from the Latin Creagra and the Greek kreourgos which means butcher, also from kreas, meat; according to Jobling it would mean "hook for meat" referring to the hooked bill of this species. [2] It was first described by French naturalist and surgeon Adolphe-Simon Neboux in 1846. Its scientific name is originally derived from the Greek word for gull, "Glaros" and via Latin Larus, "gull" and furca "two-tined fork". [3] It spends most of its life flying and hunting over the open ocean. The main breeding location is in the Galápagos Islands, particularly the rocky shores and cliffs of Hood, Tower and Wolf Islands, with lower numbers on most of the other islands. It is more common on the eastern islands where the water is warmer. [4]
It is the only fully nocturnal gull and seabird in the world, [5] preying on squid and small fish which rise to the surface at night to feed on plankton. [6]
The swallow-tailed gull has no structural or plumage differences between the male and female. In the breeding season, the adult has a black plumaged head and a bright red fleshy rim around each eye. Outside the breeding season, the head is white and the eye rim becomes black. [5] It has a grayish upper breast, gray mantle, and black wingtips. The mostly black bill has a contrasting white tip. [6]
In order to see while hunting for food at night, the swallow-tailed gull's eyes are larger in size and volume than those of any other gull. They also possess a tapetum lucidum in the back of the eye that reflects light back through the retina, increasing the amount of light available to the photoreceptor cells. [7]
A study of melatonin levels of swallow-tailed gulls found them to have no measurable daily melatonin rhythm, whereas a day-feeding gull that was chosen for comparison had the expected higher night time melatonin level for day active birds. High melatonin levels generally make birds sleepy. It is still unknown whether the melatonin levels are a cause or an effect of the swallow-tailed gulls' nocturnal activity. [8]
The swallow-tailed gull is a near-endemic breeding bird of the Galápagos Islands, although a few pairs nest on Malpelo Island off the coast of Colombia. When not breeding, it is totally pelagic, flying and hunting over the open oceans, and migrating eastward to the coasts of Ecuador and Peru.
The swallow-tailed gull is unique among the gulls in feeding exclusively nocturnally, [5] mostly on fish and squid which rise to the surface at night to feed on plankton. [6] It leaves the colony as a flock at dusk, with a great deal of screaming and display. [4]
Calls and displays are quite different from other gulls, most resembling the vocalisations of the black-legged kittiwake and Sabine's gull. The loudest and most commonly heard call is an alarm referred to as "rattle-and-whistle", a gurgling scream made with the head moving side to side. This call is contagious, with other birds joining in without seeing the cause. A loud and rapid kweek, kweek, kweek is the greeting call between mates, made with the head and neck curved forward to the ground. [4]
The swallow-tailed gull breeds from about 5 years old, [5] with pairs frequently staying together from year to year. [4] Most breed throughout the year in mixed colonies on the cliffs of the Galápagos Islands sometimes on flat areas, and food for the young is hunted from the seas near to the nesting colonies. [5] The nest is made on a small platform on a cliff, usually less than 10 m above sea level, [4] by covering the rocky ground with small pieces of lava, white coral, and sea urchin spines, which prevent the egg from rolling. [5] Nesting birds tend to face the cliff, a habit common among exclusively cliff nesting gulls, such as the black-legged kittiwake. [6] The female usually lays one speckled egg per breeding attempt. [5] [9] They are asynchronous breeders (can breed any time of the year), and follow a nine-month cycle, or less if an egg or chick is unsuccessful. [5] The egg is generally incubated for 31–34 days. [5] A chick takes its first flight at about 60–70 days old, and is fed by the adults until about 90 days, when it leaves the land, possibly with the adults, to live over the open seas. [5]
Population trends have not been estimated, but it is not thought to be threatened. The population was estimated to be about 35,000 individuals when it was last considered in 2004. [1]
Seabirds are birds that are adapted to life within the marine environment. While seabirds vary greatly in lifestyle, behaviour and physiology, they often exhibit striking convergent evolution, as the same environmental problems and feeding niches have resulted in similar adaptations. The first seabirds evolved in the Cretaceous period, and modern seabird families emerged in the Paleogene.
The Atlantic puffin, also known as the common puffin, is a species of seabird in the auk family. It is the only puffin native to the Atlantic Ocean; two related species, the tufted puffin and the horned puffin are found in the northeastern Pacific. The Atlantic puffin breeds in Russia, Iceland, Ireland, Norway, Greenland, Newfoundland and Labrador, Nova Scotia, and the Faroe Islands, and as far south as Maine in the west and France in the east. It is most commonly found in the Westman Islands, Iceland. Although it has a large population and a wide range, the species has declined rapidly, at least in parts of its range, resulting in it being rated as vulnerable by the IUCN. On land, it has the typical upright stance of an auk. At sea, it swims on the surface and feeds on zooplankton, small fish, and crabs, which it catches by diving underwater, using its wings for propulsion.
Gulls, or colloquially seagulls, are seabirds of the family Laridae in the suborder Lari. They are most closely related to the terns and skimmers and only distantly related to auks, and even more distantly to waders. Until the 21st century, most gulls were placed in the genus Larus, but that arrangement is now considered polyphyletic, leading to the resurrection of several genera. An older name for gulls is mews, which is cognate with German Möwe, Danish måge, Swedish mås, Dutch meeuw, Norwegian måke/måse and French mouette, and can still be found in certain regional dialects.
The family Procellariidae is a group of seabirds that comprises the fulmarine petrels, the gadfly petrels, the diving petrels, the prions, and the shearwaters. This family is part of the bird order Procellariiformes, which also includes the albatrosses and the storm petrels.
The common tern is a seabird in the family Laridae. This bird has a circumpolar distribution, its four subspecies breeding in temperate and subarctic regions of Europe, Asia and North America. It is strongly migratory, wintering in coastal tropical and subtropical regions. Breeding adults have light grey upperparts, white to very light grey underparts, a black cap, orange-red legs, and a narrow pointed bill. Depending on the subspecies, the bill may be mostly red with a black tip or all black. There are several similar species, including the partly sympatric Arctic tern, which can be separated on plumage details, leg and bill colour, or vocalisations.
The pigeon guillemot is a species of bird in the auk family, Alcidae. One of three species in the genus Cepphus, it is most closely related to the spectacled guillemot. There are five subspecies of the pigeon guillemot; all subspecies, when in breeding plumage, are dark brown with a black iridescent sheen and a distinctive wing patch broken by a brown-black wedge. Its non-breeding plumage has mottled grey and black upperparts and white underparts. The long bill is black, as are the claws. The legs, feet, and inside of the mouth are red. It closely resembles the black guillemot, which is slightly smaller and lacks the dark wing wedge present in the pigeon guillemot.
The common murre also called the common guillemot or foolish guillemot,(Uria aalge) is a large auk. It has a circumpolar distribution, occurring in low-Arctic and boreal waters in the North Atlantic and North Pacific. It spends most of its time at sea, only coming to land to breed on rocky cliff shores or islands.
The ivory gull is a small gull, the only species in the genus Pagophila. It breeds in the high Arctic and has a circumpolar distribution through Greenland, northernmost North America, and Eurasia.
Forster's tern is a tern in the family Laridae. The genus name Sterna is derived from Old English "stearn", "tern", and forsteri commemorates the naturalist Johann Reinhold Forster.
The red-legged kittiwake is a seabird species in the gull family Laridae. It breeds in the Pribilof Islands, Bogoslof Island, and Buldir Island in the Bering Sea off the coast of Alaska, and the Commander Islands, Russia, and spends the winter at sea.
The black-legged kittiwake is a seabird species in the gull family Laridae.
The ashy storm petrel is a small, scarce seabird of the storm petrel family Hydrobatidae. It breeds colonially on islands off the coasts of California and Mexico, and is one of six species of storm petrel that live and feed in the rich California Current system.
The Galápagos hawk is a large hawk endemic to most of the Galápagos Islands.
The brown noddy or common noddy is a seabird in the family Laridae. The largest of the noddies, it can be told from the closely related black noddy by its larger size and plumage, which is dark brown rather than black. The brown noddy is a tropical seabird with a worldwide distribution, ranging from Hawaii to the Tuamotu Archipelago and Australia in the Pacific Ocean, from the Red Sea to the Seychelles and Australia in the Indian Ocean and in the Caribbean to Tristan da Cunha in the Atlantic Ocean. The brown noddy is colonial, usually nesting on elevated situations on cliffs or in short trees or shrubs. It only occasionally nests on the ground. A single egg is laid by the female of a pair each breeding season. In India, the brown noddy is protected in the PM Sayeed Marine Birds Conservation Reserve.
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The Antarctic tern is a seabird in the family Laridae. It ranges throughout the southern oceans and is found on small islands around Antarctica as well as on the shores of the mainland. Its diet consists primarily of small fish and crustaceans. It is very similar in appearance to the closely related Arctic tern, but it is stockier, and it is in its breeding plumage in the southern summer, when the Arctic tern has shed old feathers to get its non-breeding plumage. The Antarctic tern does not migrate like the Arctic tern does, but it can still be found on a very large range. This tern species is actually more closely related to the South American tern.
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