Crown shard

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Crown shard
Crown scar, Stoney Point, South Africa

Crown scar, Stoney Point, South Africa

Systematics
Sub-stem : Vertebrates (vertebrata)
Class : Birds (aves)
Order : Suliformes
Family : Cormorants (Phalacrocoracidae)
Genre : Microcarbo
Type : Crown shard
Scientific name
Microcarbo coronatus
( Wahlberg , 1855)

The crown shag ( Microcarbo coronatus , Syn . : Phalacrocorax coronatus ) is a species of bird from the cormorant family . Like the closely related sedge, the crown shag is one of the smallest members of the family. It is endemic to the waters of the Benguela Current off the west coast of southern Africa . The IUCN carries the crown claw at the early warning level ( near threatened ).

description

Crown shags are 50–55 cm long and weigh about 400 g. The plumage of adult birds is almost completely black with fine white speckles on the ear covers and a reddish area in front of the eye. On the forehead, the birds have a clear forehead, which is missing in young birds. These generally have a rather brown plumage. They can be distinguished from immature sedge by their darker underside and shorter tail.

The iris of the birds is red, like that of sedge, the lower beak dark yellow, the upper beak rather brownish.

distribution

The nearly 50 colonies of the crown shag can be found along the Atlantic coast of southern Africa south to Cape Agulhas north to Walvis Bay and Swakopmund . Since the turn of the millennium there has also been a small colony about 300 km east of Cape Agulhas in the Tsitsikamma National Park and thus on the coast of the Indian Ocean. The birds are found exclusively on the coast and have never been seen at a distance of 10 km from the coast or 100 m inland.

The total population is around 3000 breeding pairs. Ring finds have shown that the young birds move up to almost 300 km from the nest location. Adult birds also migrate between colonies, which can be up to 500 km apart.

Way of life and reproduction

Crown shags feed mostly (97%) on small fish (6–16 cm), in particular clipfish and pipefish , and to a small extent on invertebrates that are hunted in shallow coastal waters and in the kelp forest .

The birds do not have a strictly defined breeding season and lay eggs at any time of the year. However, the majority of broods take place in the spring and summer of the southern hemisphere. The nest is built from kelp , sticks, bones etc. and lined with kelp or feathers. Most of the time, the nest is built on an elevated structure such as rocks or trees, but man-made structures are also used. In exceptional cases, nests are also built on the ground. The individual colonies are rather small and typically consist of fewer than 150 individuals. However, the crown shags often socialize with other colony breeders.

As a rule, three eggs are laid an average of two days apart. The breeding season averages 23 days. After at least 35 days, the young birds are fully fledged, whereby mostly only two of the three chicks survive due to the asynchronous hatching and the resulting size difference.

Systematics

The species was first described by Johan August Wahlberg in 1855 as Graculus coronatus in Namibia. The generic name Graculus literally means "jackdaw". Later the species was assigned to the large genus Phalacrocorax and listed there as a subspecies of the very similar sedge. However, together with the dwarf shear , the Mohrenscharbe , the reed shear and the crinkle shear , it puts newer systematics in the genus Microcarbo (literally "small sharks").

The species is monotypical , i.e. H. no subspecies are distinguished.

Danger

Clutches and young birds that do not fly are threatened by various other bird species such as the Dominican gull and the great white pelican. Human influences that have a negative effect on the stock situation include: a. Oil spills, plastic spills, commercial fishing and resulting ghost nets, and all sorts of other spills and disruptions. Human disturbances often lead to temporary abandonment of the clutch and hasty flight of the young birds, which makes predation by predators more likely. For these reasons and because of the relatively small total population, the IUCN placed the species in the early warning level ( near threatened ) despite the stable population size .

literature

  • Ian Sinclair, Phil Hockey, Warwick Tarboton: SASOL Birds of Southern Africa . Struik, 2002, ISBN 1-56098-216-0 .
  • Paul A. Johnsgard: Cormorants, Darters, and Pelicans of the World . Smithsonian Institution Press, Washington 1993, ISBN 1-56098-216-0 , pp. 152-155 .
  • PAR Hockey, WRJ Dean, PG Ryan: Roberts Birds of Southern Africa . 7th edition. Trustees of the John Voelcker Bird Book Fund, Cape Town 2005, ISBN 0-620-34053-3 , pp. 149-151 .

Web links

Commons : Kronenscharbe ( Microcarbo coronatus )  - Collection of images, videos and audio files

Individual evidence

  1. ↑ a b c J. Orta, F. Jutglar, EFJ Garcia, GM Kirwan, P. Boesman: Crowned Cormorant (Microcarbo coronatus). In: J. del Hoyo, A. Elliott, J. Sargatal, DA Christie, E. de Juana (Eds.): Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona 2018. (accessed on https://www.hbw.com/node/52661 on July 20, 2018).
  2. ^ PA Whittington: New breeding locality for Crowned Cormorant . In: Koedoe . No. 47 , 2004, p. 125-126 .
  3. ↑ A. Williams, J. Cooper: The Crowned Cormorant: breeding biology, diet, and offspring reduction strategy. In: Ostrich. Volume 54, 1983, pp. 213-219.
  4. ^ D. Siegel-Causey: Phylogeny of the Phalacrocoracidae . In: Condor . tape 90 , no. 4 , 1988, pp. 885-905 , doi : 10.2307 / 1368846 ( unm.edu [PDF]).
  5. ^ List of bird names in the IOU IOC World Bird List
  6. ^ IUCN website Red List of Endangered Species , Threats section