shag
| shag | ||||||||
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Common crow ( Phalacrocorax aristotelis ) |
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| Systematics | ||||||||
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| Scientific name | ||||||||
| Phalacrocorax aristotelis | ||||||||
| ( Linnaeus , 1758) |
The Shag ( Phalacrocorax aristotelis ) is a bird from the family of cormorants . Shags differ from the closely related species of cormorant ( Phalacrocorax carbo ) in that they have no white on the body.
description
Shags reach a body length of 66 to 76 centimeters and a wingspan of 122 centimeters. The main plumage is glossy greenish-black. The breeding plumage is noticeable: The crown feathers are then elongated and form a head turned forward.
The shag's beak and feet are black, the bare skin around the beak is yellow and the throat is black with yellow spots.
distribution
Three poorly differentiated subspecies are distinguished: The nominate form Phalacrocorax aristotelis aristotelis occurs in northern and western Europe. The subspecies P. a. riggenbachi colonizes northwest Africa and the subspecies P. a. desmarestii inhabits the Mediterranean and the Black Sea.
In Central Europe, the nominate form is annual and the subspecies P. a. desmarestii occasional guest bird. It occurs singly or in small numbers on the North Sea coast of Belgium, the Netherlands and Germany and can also occasionally be observed in the German Bight around Heligoland.
The species is a resident and partial migrant . The colonies in northern Europe show larger dispersal migrations. This is presumably due to stronger food and weather influences. Food shortages in particular can result in massive emigration. However, individual shags are also devoured by storms.
Reproduction
The males of the common crow breed for the first time at three, the females at four. They lead a monogamous seasonal marriage , but loss of brood can lead to a change of partner. In a study on partner stability, around every third couple separated each year. The nest is in rocky coastal areas. Shags breed in colonies, but they show greater nest spacing than cormorants. The nesting material is usually brought in by the male, and both parent birds block it.
The laying time falls from March / April to May / June. The clutches contain between one and six eggs, most clutches have three eggs. Breeding begins with the second egg. Both parent birds breed and feed and the nestling period averages 53 days. The young birds continue to be fed by the parent birds for at least twenty days after they have left the nest.
supporting documents
literature
- Hans-Günther Bauer, Einhard Bezzel and Wolfgang Fiedler (eds.): The compendium of birds in Central Europe: Everything about biology, endangerment and protection. Volume 1: Nonpasseriformes - non-sparrow birds. Aula-Verlag Wiebelsheim, Wiesbaden 2005, ISBN 3-89104-647-2 .
Web links
- Gulosus aristotelis in the endangered Red List species the IUCN 2008. Posted by: FM Parauka, 2008. Accessed January 30 of 2009.
- Videos, photos and sound recordings of Phalacrocorax aristotelis in the Internet Bird Collection
- Feathers of the shag
Single receipts
- ↑ Bauer et al., P. 237
- ↑ Bauer et al., P. 238
- ^ Joan Roughgarden : Evolution's Rainbow: Diversity, Gender, and Sexuality in Nature and People. University of California Press, Berkeley 2004, ISBN 0-520-24073-1 , p. 55
- ↑ Bauer et al., P. 239