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Institut de recherche pour la conservation des zones humides méditerranéennes

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Titre :	Status of the Baltic/Wadden Sea population of the Common Eider Somateria m. mollissima.
Auteurs :	M. Desholm, Auteur ; T. K. Christensen, Auteur ; G. Scheiffarth, Auteur ; M. Hario, Auteur ; A. Andersson, Auteur ; B. Ens, Auteur ; C. J. Camphuysen, Auteur ; L. Nilsson, Auteur ; C. M. Waltho, Auteur ; S.-H. Lorentsen, Auteur ; A. Kuresoo, Auteur ; R. K. H. Kats, Auteur ; D. M. Fleet, Auteur ; A. D. Fox, Auteur
Type de document :	Article
Dans :	Wildfowl (53 2002)
Article en page(s) :	167-203
Langues:	Anglais
Résumé :	A dramatic decline in the number of wintering Common Eiders from c. 800,000 to c. 370,000 occurred in Danish waters between 1990 and 2000. Denmark represents the second most important wintering area for Eiders from the Baltic/Wadden Sea flyway, and mid-winter counts suggest the total population could have fallen from c.1.2 million individuals in 1991 to c. 760,000 in 2000, implying major (c.36%) overall declines. However, although declines of similar magnitude have been detected in breeding numbers at some sites (eg Saltholm in Denmark), such a dramatic reduction is not generally evident amongst breeding numbers monitored throughout the flyway. Five hypotheses are offered to explain this discrepancy, two of which are considered likely to contribute to the differences. These relate to shortcomings in our ability to monitor adequately breeding and wintering numbers in both time and space, as well as to an unknown buffering effect of non-breeders (which are counted on the winter quarters, but which do not appear amongst assessments of breeding abundance). Parameters known to contribute to declines in population size include low duckling survival caused by viral infections, mass adult mortality due to Avian Cholera, and reduced adult annual survival rates due to mass mortality events on the wintering grounds. The population continues to be a quarry species in Denmark, Sweden, Norway and Finland. It is strongly recommended that the national monitoring schemes should be standardised and synchronised, in order to establish future population abundance and change. It is further recommended that population modelling is undertaken to understand the relationships between the numbers of Common Eiders in the Baltic/Wadden Sea flyway population and the different factors affecting their abundance.

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