Lava gull
| Lava gull | ||||||||||||
|---|---|---|---|---|---|---|---|---|---|---|---|---|
Pair of lava gulls on a boat near the Galapagos Islands |
||||||||||||
| Systematics | ||||||||||||
|
||||||||||||
| Scientific name | ||||||||||||
| Leucophaeus fuliginosus | ||||||||||||
| ( Gould , 1841) |
The lava gull ( Leucophaeus fuliginosus , syn .: Larus fuliginosus ) is a species of the gulls (Larinae). It occurs exclusively on the Galapagos Islands and is considered the rarest species of seagull in the world, with an estimated 300–600 individuals. The IUCN has therefore classified the species as endangered.
features
The lava gull is a medium-sized species of gull. It is slim built, has a short neck with a sharply pointed head. The wings are longer and more pointed than most other gulls. Their tail is fan-shaped, their feet have one short and three long toes. This species is predominantly gray in color. Her head, throat, and neck are dark brown. The wings are dark to slate gray, the tips of the umbrella feathers are white and the wings are black. The neck and chest are medium gray in color, the belly is light gray. The lava gull has a completely black tail on the upper side, the tail underside is white. The plumage is mostly brown in color when young. The wings are dark brown, the rest of the body gray-brown. The lava gull has a red eye ring, above and below the eye there is a white spot. The beak and feet are slate gray in all the bird's clothes, the oral cavity is bright red. The lava gull reaches a body length of 41 centimeters.
distribution and habitat
The lava gull is one of the bird species endemic to the Galapagos Islands . The main areas of distribution in 2015 were the vicinity of the ports of Santa Cruz , Isabela and San Cristóbal , as well as the uninhabited island of Genovesa . The breeding of the animals was observed on a total of 12 islands in the archipelago. The lava gull is a resident bird . Flights between the islands of the Galapagos Archipelago up to a distance of 130 kilometers are occupied; however, long flights over the open sea are rare.
The lava gull prefers sandy and pebbly beaches near food sources such as seabird colonies or harbors. The largest number of lava gulls to date has been recorded at Academy Bay on Santa Cruz Island.
Way of life
nutrition
The lava gull mainly eats fish , crustaceans , molluscs and even algae . The bird also finds garbage and carrion in harbors and follows fishing cutters to get some remains of the fish. Less often he hunts small lizards such as geckos and young marine iguanas .
A 2015 study of lava gulls on Genovesa Island highlights the species' kleptoparasitism . Apparently the animals take advantage of attacks by the magnificent frigate bird ( Fregata magnificens ) on other seabirds in order to catch prey that has been dropped in flight or to exploit the confusion in the context of nest attacks to steal food.
Reproduction
The lava gull does not breed in colonies, but sporadically. She prefers sandy beaches and lays the nest at a distance of 5 to 50 meters from the high tide mark. The nest is built between plants such as Cryptocarpus pyriformis in a natural hollow on the ground. It is cone-shaped, made of soil, waste and twigs and is padded with parts of plants.
The female usually lays two olive to pale brown eggs with gray or dark brown spots, which both sexes incubate for about 33 days. The chicks stay in the immediate vicinity of the nest for the first 2-3 days and then move further away from the nest, but remain under the protection of the vegetation. They get choked and pre-digested food from their parents. After about seven and a half weeks, the young birds fledge, but stay with their parents for almost another three weeks. The breeding birds are very vigilant during the breeding season and leave the nest as soon as the potential nest predator is only one kilometer away.
Persistence and Threat
In 1963 the total number was estimated at 300–400 pairs. This estimate was based on a count along a stretch of coastline from Santa Cruz, which was then extrapolated to the entire coastline of the Galapagos Islands. However, since the entire coast does not have suitable breeding sites, this population was soon assumed to be too high. Assuming a population size of 78–81 individuals in the south of Santa Cruz and 20–29 individuals on Genovesa, as well as the assumption that the population on San Cristóbal and Isabela is similar, but not twice as large, a total population of 300-600 individuals assumed.
The only natural enemies of the lava gull are adult marine iguanas that sometimes eat nestlings. Other threats are introduced rats , domestic cats and stray dogs .
literature
- J. Burger / M. Gochfeld / EFJ Garcia / GM Kirwan: Lava Gull (Larus fuliginosus) , in: J. del Hoyo et al. (Ed.), Handbook of the Birds of the World Alive, Barcelona 2015 (last accessed September 12, 2015)
Remarks
- ↑ a b c K. Thalia Grant / Olivia H. Estes / Gregory B. Estes, Observations on the breeding and distribution of Lava Gull Leucophaeus fuliginosus , in: Cotinga 37 (2015), pp. 22-35, here p. 35.
- ^ Thalia Grant / Estes / Estes, Observations on the breeding and distribution of Lava Gull , p. 34.
- ↑ a b c d e f Burger et al., Lava Gull (Larus fuliginosus) , in: Handbook of the Birds of the World Alive.
- ^ Thalia Grant / Estes / Estes, Observations on the breeding and distribution of Lava Gull , p. 33.
- ↑ Thalia Grant / Estes / Estes, Observations on the breeding and distribution of Lava Gull , p. 32.
- ↑ Barbara K. Snow / David W. Snow , Observations on the Lava Gull Larus fuliginosus , in: Ibis 111 (1969), pp. 30-35.
