La Tour du Valat

Institut de recherche pour la conservation des zones humides méditerranéennes

Titre :	Why Afro-Siberian Red Knots Calidris canutus canutus have stopped staging in the western Dutch Wadden Sea during southward migration
Auteurs :	Casper Kraan, Auteur ; Jan A. van Gils, Auteur ; Bernard Spaans, Auteur ; Anne Dekinga, Auteur ; Theunis Piersma, Auteur
Type de document :	Article
Dans :	Ardea (98(2) FAL 2010)
Article en page(s) :	155-160
Résumé :	Afro-Siberian Red Knots Calidris canutus canutus use the western Dutch Wadden Sea as a refuelling area during southward migration from Taimyr to West Africa. Here we document the decline of their food stocks in this area, based on a yearly large-scale benthic mapping effort, from 1996 to 2005. For each benthic sampling position, intake rate (mg/s, ash-free dry mass) was predicted by an optimal diet model based on digestive rate maximization. Over the ten years, when accounting for a threshold value to meet energetic fuelling demands, subspecies canutus lost 86% of its suitable foraging area. Over this period, the proportion of probable canutus in mist-net catches in July-August declined relative to overwintering islandica Knots. This suggests that canutus dropped even more in numbers than islandica, for which we showed earlier a food-explained decline in numbers. We discuss the possible causality between a decline in the quality of intertidal mudflats in the Dutch Wadden Sea and population declines of Knots in the West-African wintering quarters.

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