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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Identification of breeding female Common Cranes Grus grus through their clutches
Auteurs :	Wolfgang Mewes, Auteur ; Moriz Rauch, Auteur
Type de document :	Article
Dans :	Vogelwelt (Die) (131(2) 2010)
Article en page(s) :	93-102
Résumé :	Investigation of selected Common Crane breeding pairs in a 338 km(2) area in the district of Parchim (Mecklenburg-Western Pomerania) comprised nest monitoring, egg measurements (size and weight) and photography. At many breeding sites clutches resemble those of recent years and revealed typical characteristics. Hence, a resultant method was created to identify female cranes by their clutches. Features for female identification were egg length, diameter and shape as well as basic colour and spots on egg shells. In addition, analysis focused on the dispersal, shape, size, colour and density of the spots on egg shells. Between 1988 and 2009 the authors examined 1,144 eggs from 697 clutches. Crane eggs averaged 9.65 cm +/- 4.9% in length, 6.16 cm +/- 3.6% in diameter and 201 g +/- 9.5% in weight (fresh state). For individual females, variation amounted to +/- 4.9% in egg length and to +/- 3.2% in egg width. Different types of colouration and mottling are described and illustrated in this study. Moreover it is shown that 85% of the females from 200 examined locations sticked to their favoured breeding areas between 2006 and 2009. In 15% of these areas new females were observed. In addition, this method facilitates distinctions of first and subsequent clutches from selected females. Between 2006 and 2009 three females had three (two subsequent) clutches each in one year. As third implementation age determination and changes of female cranes were documented within 21 years. In 2009 the two oldest females alive were at least 23 years old. Hereafter genetic analysis of crane eggs will be arranged to verify the results of this study and the relationship among females with very similar clutches.

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