Chatham Shear
| Chatham Shear | ||||||||||||
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| Leucocarbo onslowi | ||||||||||||
| ( Forbes , 1893) |
The Chatham shear ( Leucocarbo onslowi , Syn . : Phalacrocorax onslowi ) is a species of bird from the genus Phalacrocorax within the cormorant family . The species occurs only along the coasts of to New Zealand belonging Chatham Islands before. It breeds in small colonies and feeds primarily on fish . The IUCN lists the species because of the increasing destruction of its habitat and the small population as " Critically Endangered ". BirdLife International estimates the existence of the Chatham shear at only 540 sexually mature individuals. As with many cormorants, the species status is controversial.
Appearance
Chatham scars reach a maximum length of 63 centimeters and a weight between 1790 and 2525 grams. The species shows a sexual dimorphism , the males are slightly larger and heavier than the females. The species is very similar to the larger warthog , but shows a little less white on the wings as well as a red beak base and an equally colored facial skin that extends around the eye. The bare facial skin above the upper beak base has pronounced, warty outgrowths that are yellow in color, especially during the breeding season. The gray bill is shorter and narrower in relation to the body mass than that of the warthog. The iris is blue in color, legs and feet are pink.
Young birds are already very similar to adult birds, but they have brown instead of black feathers. The white wing markings of adult birds can already be indicated by lighter feathers in this area.
The Chatham Shear cannot be confused with any other species within its range: It is the only species of cormorant that occurs on this archipelago that has a white underside and pink feet. The chatham shear does not socialize with any other species of cormorant.
distribution and habitat
The Chatham Shag is an endemic of to New Zealand belonging Chatham Islands . The occurrence is limited to the shallow coastal waters and bays; it is not found on the high seas .
The species is a resident bird and young birds show no tendency to dismigrate .
food
The diet consists mainly of small fish , but nothing is known about the exact composition. Like all cormorants, the species prefers to hunt its prey by diving, following and catching it while swimming underwater. Occasionally some birds band together to hunt together.
Since the plumage of the Chatham Shark absorbs water, it must be dried after a dive. Like most cormorants, the species spreads its wings and lets the sun or wind dry its plumage.
Breeding and breeding behavior
So far, little information is available about the reproductive biology of the Chatham shear. The start of the breeding season is between September and December and depends on the food supply.
The species breeds in small colonies on rocky coastlines and offshore rock islands. The nest, which mainly consists of small sticks, algae and grass , is preferably built on flat slopes or level ground and consolidated with excrement .
Usually three eggs are laid. The chicks hatch naked, and after a few days they grow into a brown down dress . Young chatham shags are occasionally so harassed by herring headed gulls that they choke up their food.
Systematics
As with all cormorants, the exact systematic position of the species is disputed. The chatham shear belongs to a group of cormorant species in the southern hemisphere, which are divided into different species due to their often small morphological differences. The correctness of this approach is disputed. A final clarification of the system using genetic methods is still pending. The chatham shear is considered by some scientists to be a subspecies of the warthog .
Hazard and protection
The IUCN lists the species as " Critically Endangered " because the total population is estimated to be less than 500 animals and has declined sharply in recent years. Threats are the disturbance of the breeding colonies by agriculture as well as stalking by feral domestic cats and introduced rats . Due to the small distribution area, the species can only very slowly compensate for losses.
References
literature
- Josep del Hoyo , Andrew Elliot, Jordi Sargatal : Handbook of the birds of the world. Volume 1: Ostrich to Ducks. Lynx Edicions, Barcelona 1992, ISBN 84-87334-10-5 .
- PJ Higgins (Ed.): Handbook of Australian, New Zealand & Antarctic Birds , Volume 1, Ratites to Ducks, Oxford University Press, Oxford 1990, ISBN 0195530683
Web links
Individual evidence
- ↑ Leucocarbo onslowi in the endangered Red List species the IUCN 2010. Posted by: BirdLife International, 2010. Accessed March 16, 2011th
- ↑ BirdLife International on Chatham Shear , accessed May 14, 2011
- ^ Higgins, p. 881
- ^ Higgins, p. 882
- ^ Higgins, p. 882