| 词条 | Kelp gull | |||||||||||
| 释义 |
| name = Kelp gull | status = LC | status_system = IUCN3.1 | status_ref = [1] | image = {{Css Image Crop|Image = SouthShetland-2016-Livingston Island (Hannah Point)–Kelp gull (Larus dominicanus).jpg|bSize = 475|cWidth = 235|cHeight = 235|oTop = 50|oLeft = 85|Location = center}} | image_caption = Adult in Livingston Island, South Shetland Islands | genus = Larus | species = dominicanus | authority = Lichtenstein, 1823 }} The kelp gull (Larus dominicanus), also known as the Dominican gull, is a gull which breeds on coasts and islands through much of the southern hemisphere. The nominate L. d. dominicanus is the subspecies found around South America, parts of Australia (where it overlaps with the Pacific gull), and New Zealand (where it is known as the southern black-backed gull, simply the black-backed gull, or by its Māori name karoro). L. d. vetula (known as the Cape gull) is a subspecies occurring around southern Africa. The specific name comes from the Dominican Order of friars, who wear black and white habits.[2] DescriptionThe kelp gull superficially resembles two gulls from further north in the Atlantic Ocean, the lesser black-backed gull and the great black-backed gull and is intermediate in size between these two species. This species ranges from {{convert|54|to|65|cm|in|abbr=on}} in total length, from {{convert|128|to|142|cm|in|abbr=on}} in wingspan and from {{convert|540|to|1390|g|lb|abbr=on}} in weight. Adult males and females weigh on average {{convert|1000|g|lb|abbr=on}} and {{convert|900|g|lb|abbr=on}} respectively. Among standard measurements, the wing chord is {{convert|37.3|to|44.8|cm|in|abbr=on}}, the bill is {{convert|4.4|to|5.9|cm|in|abbr=on}} and the tarsus is {{convert|5.3|to|7.5|cm|in|abbr=on}}.[3][4][5] The adult kelp gull has black upperparts and wings. The head, underparts, tail, and the small "mirrors" at the wing tips are white. The bill is yellow with a red spot, and the legs are greenish-yellow (brighter and yellower when breeding, duller and greener when not breeding). The call is a strident ki-och. Juveniles have dull legs, a black bill, a dark band in the tail, and an overall grey-brown plumage densely edged whitish, but they rapidly get a pale base to the bill and largely white head and underparts. They take three or four years to reach maturity. SubspeciesThere are five subspecies of kelp gull. The African subspecies L. d. vetula is sometimes split as the Cape gull, L. vetula. It has a more angular head and a smaller shorter bill. The adult has a dark eye, whereas the nominate kelp gull usually has a pale eye. Young Cape gulls have almost identical plumage to similarly aged kelp gulls.
BehaviourKelp gulls are omnivores like most Larus gulls, and they will scavenge as well as seek suitable small prey. They gather on landfills and a sharp increase in population is therefore considered as an indicator for a degraded environment.[6] Kelp gulls have been observed feeding on live right whales since at least 1996.[7] The kelp gull uses its powerful beak to peck down centimetres into the skin and blubber, often leaving the whales with large open sores, some of which have been observed to be half a meter in diameter. This predatory behavior has been documented in Argentinian waters, and continues today.[8] At rocky sites along the southern African coast, such as at Boulders Beach in Cape Town, kelp gulls (Larus dominicanus vetula) can be seen picking up shellfish and repeatedly flying up several meters and dropping them onto the rocks below in order to break them open.[9] They have also been reported pecking the eyes out of seal pups on the coast of Namibia before attacking the blind seals in a group.[10] The nest is a shallow depression on the ground lined with vegetation and feathers. The female usually lays 2 or 3 eggs. Both parents feed the young birds. GalleryCape gull (Larus dominicanus vetula or Larus vetula)The Cape gull differs from other forms of kelp gulls by its immaculate white tail and dark eye. ==References== 1. ^{{IUCN|id=22694329 |title=Larus dominicanus |assessor=BirdLife International |assessor-link=BirdLife International |version=2013.2 |year=2012 |accessdate=26 November 2013}} * Ian Sinclair, Phil Hockey and Warwick Tarboton, SASOL Birds of Southern Africa (Struik 2002) {{ISBN|1-86872-721-1}}{{Commons category|Larus dominicanus}}{{Wikispecies|Larus dominicanus}}2. ^"Shelly Farr Biswell", "Southern Black-Backed Gulls", New Zealand Geographic, number 73, May–June 2005 3. ^Gulls: Of North America, Europe, and Asia by Klaus Malling Olsen & Hans Larsson. Princeton University Press (2004). {{ISBN|978-0691119977}}. 4. ^Harrison, Peter, Seabirds: An Identification Guide. Houghton Mifflin Harcourt (1991), {{ISBN|978-0-395-60291-1}} 5. ^CRC Handbook of Avian Body Masses by John B. Dunning Jr. (Editor). CRC Press (1992), {{ISBN|978-0-8493-4258-5}}. 6. ^Cf. José Felipe M. Pereira, Aves e Pássaros Comuns do Rio de Janeiro, Rio de Janeiro: Technical Books, {{ISBN|978-85-61368-00-5}}, pg.55 7. ^[https://archive.today/20130105065559/http://www3.interscience.wiley.com/journal/119942735/abstract?CRETRY=1&SRETRY=0 Increased harassment of Right Whales (Eubalaena australis) by Kelp Gulls (Larus dominicanus) at Península Valdés, Argentina]. Rowntree, V.J., P. MacGuiness, K. Marshall, R. Payne, J. Seger, and M. Sironi, 1998. Marine Mammal Science. 14(1): 99 - 115. {{doi|10.1111/j.1748-7692.1998.tb00693.x}} 8. ^Gulls' vicious attacks on whales. BBC News, June 24, 2009. 9. ^Siegfried WR (1977) Mussel dropping behaviour of Kelp Gulls. S Afr J Sci 73:337 - 341 10. ^{{cite web|last1=Bittel|first1=Jason|title=Seagulls Have a Gruesome New Way of Attacking Baby Seals|url=http://news.nationalgeographic.com/2015/08/150817-seals-seagulls-animals-science-predators-prey/|website=National Geographic|accessdate=4 September 2015}} External links
8 : Larus|Birds of Antarctica|Birds of Patagonia|Birds of Madagascar|Birds of Southern Africa|Birds of the Southern Ocean|Fauna of subantarctic islands|Birds described in 1823 |
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