Lummenalk
| Lummenalk | ||||||||||
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Lummenalk ( Synthliboramphus hypoleucus ) |
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| Scientific name | ||||||||||
| Synthliboramphus hypoleucus | ||||||||||
| ( Xantus , 1860) |
The Lummenalk ( Synthliboramphus hypoleucus ) is a small species from the family of alken birds . Within this family, the Lummenalk, which occurs in the northern Pacific , has one of the southernmost ranges. It breeds on islands off the coast of California and Mexico . Although this species has a very small range, two subspecies are described.
The IUCN classifies the Lummenalk as endangered ( vulnerable ) because of its limited occurrence and the decline in the population in recent years .
Appearance
The Lummenalk is one of the smallest with a body length of 24 cm and also a relatively slender alken bird with black and white plumage. There is no seasonal difference in plumage. The legs are set very far back on the body, so that it moves very clumsily on land. The average weight of breeding birds is 171 g, with females being slightly heavier than males.
The top is completely black. Freshly moulted plumage has a slightly bluish sheen, worn plumage looks grayish. The underside of the body is white. The small and pointed beak is black. The legs and toes are slightly bluish, the webbed feet are black, and the iris is brown. Guillemot fly with rapid wing beats. They can fly up from the surface of the water without making a running start.
Young birds are similar to adult birds, but have indistinct horizontal stripes on the flanks and a slightly shorter beak than adult birds.
Within its range, the Lummenalk can be confused with the Craverialk and, in winter, with the Marmelalk . The pure white underside of the body and the lighter lower wings distinguish the Lummenalk from these two species. Marmalks also have a significantly shorter beak.
Distribution area
Together with the Craverialk, this species has the southernmost distribution areas of all the alken birds. The breeding areas are on the California Channel Islands , on Guadalupe and on other islands off the coast of Lower California . The Lummenalk can therefore be found in bodies of water whose surface temperature is more than 12 degrees Celsius. Outside of the breeding season, it lives in the open sea, to the north the distribution extends to the area of British Columbia .
food
When diving for food, guillemot often follows larger predatory fish, such as tuna , and catches smaller fish in the process. When diving, the birds use their wings, which propel them forward with powerful strokes. Guillemot are often seen in pairs outside of the breeding season and it is believed that they also hunt together.
During the breeding season, the guillemot's feeding grounds are close to their breeding grounds, mostly above the continental shelves . Detailed studies off the California coasts have shown that guillemot can be found in spring and summer mainly between the 35th and 43rd parallel north. Their range is greater during autumn. They are then usually more than 50 kilometers away from the coastline.
Reproduction
The colonies are found on small, precipitation-poor islands with sparse and mostly thorny vegetation. Most of the colonies are less than 200 meters from the coastline. The breeding site loyalty is high. In one study, the majority of the ringed breeding birds used the same nesting site for three years in a row. The individual nests are differently far apart, which is rather unusual for alken birds, which often breed in dense colonies. Guillemot are also one of the few alkenbirds with clutches. There are also twelve documented cases in which second broods occurred.
Guillemot breeds in small caves, in rock niches or under bushes in open colonies. They also use abandoned burrows of rabbits and owls . Later in the year, petrels occasionally use guillemot burrows for their brood. The propagation time is relatively little synchronized. On Santa Barbara Island , a study found that guillemot lay 80 percent of eggs over a period of 24 to 47 days. The earliest oviposition on this island took place on February 22nd, the peak of the oviposition fell in the period from March 21st to April 21st. The last eggs were laid in mid-June. The eggs are elliptical to oval and on a whitish to olive-brown background, gray and brown speckled and roughly speckled. On Santa Barbara Island 69 percent of the nests had two eggs, 25 percent of the clutches consisted of one egg. Larger clutches were also found, but this is probably a nest used by two or more females. The eggs usually begin to incubate two days after the second egg is laid. The incubation period is on average 31 days. Young birds weigh an average of 23.8 grams when they hatch. They are huddled until they leave the nest and leave it on the second day after hatching.
Guillemots raised in captivity changed their behavior significantly 48 hours after hatching. While they remained quiet in their nest up to this point, they showed a very agile behavior afterwards and ran around excitedly in their nesting boxes. Under natural conditions, at this point in time, they are led by their parent birds on the high seas. By then you are already very good swimmers and able to climb over obstacles on land. Their further development on the high seas has not yet been documented. Guillemot birds reared in captivity showed only very slow weight gain and a change in plumage only on the 17th day of life.
On Santa Barbara Island, an average of 72 fledglings per 100 nests fledged. White footed mice are responsible for around 44 percent of egg losses. Another 14 percent of the clutches were abandoned by the adult birds. The predators of guillemots that beat adults and young birds include mammals introduced to the islands, barn owls , western gulls and peregrine falcons . Some adult guillemots also die because they become entangled in vegetation on land. Since several adult guillemotons which had reached an age of more than 14 years were caught, it is assumed that the mortality rate of breeding birds is relatively low.
Duration
The inventory is difficult with this species because the nesting sites are far apart and the Lummenalk lives very hidden. The total population is estimated to be less than 10,000 birds, making the Lummenalk one of the most endangered alks.
Marine pollution is the guillemotion's greatest threat. Much of the total population lives in the heavy tanker area of Los Angeles , so a single disaster could be devastating. Introduced animals such as rats and feral cats also pose a great danger. The abandonment of individual islands off Baja California as breeding areas and the significant decline on other islands is probably due to the latter. On the Anacapa Island , the rats introduced there were successfully disposed of with the help of poisoned bait. Guillemots are attracted to ship lights and therefore often collide with ships. In addition, ships anchored in the vicinity of breeding colonies have significantly disrupted breeding activities.
Subspecies
Two subspecies are described for this species:
- S. h. scrippsi ( Xantus de Vesey , 1860) is the northern subspecies. It differs from the nominate form in that it has a more white face. The white line that runs over the eye is striking.
- S. h. hypoleucus ( Green & Arnold , 1939) breeds on the islands off the west coast of Baja California .
supporting documents
literature
- Jonathan Alderfer (Ed.): National Geographic complete Birds of Northamerica. National Geographic, Washington DC 2006, ISBN 0-7922-4175-4 .
- Anthony J. Gaston, Ian L. Jones: The Auks (= Bird Families of the World. Vol. 4 (recte 5)). Oxford University Press, Oxford u. a. 1998, ISBN 0-19-854032-9 .
Web links
- Synthliboramphus hypoleucus in the endangered Red List species the IUCN 2008. Posted by: BirdLife International, 2008. Accessed January 31 of 2009.
Single receipts
- ↑ BirdLife Factsheet on the Lummenalk , accessed on October 17, 2010
- ↑ BirdLife Factsheet on the Lummenalk , accessed on October 17, 2010
- ↑ Gaston et al., P. 205
- ↑ Alderfer, p. 288
- ↑ Gaston et al., P. 208
- ↑ Gaston et al., P. 208
- ↑ Gaston et al., P. 211
- ↑ Gaston et al., P. 209
- ↑ Gaston et al., P. 209
- ↑ Gaston et al., P. 209
- ↑ Gaston et al., P. 209
- ↑ Gaston et al., P. 210
- ↑ Gaston et al. P. 210
- ↑ Gaston et al., P. 210
- ↑ Gaston et al., P. 211
- ↑ Gaston et al., P. 207 and p. 208