Why Afro-Siberian Red Knots Calidris canutus canutus have stopped staging in the western Dutch Wadden Sea during southward migration
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 e...
Published in: | Ardea |
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Main Authors: | , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
2010
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Subjects: | |
Online Access: | https://hdl.handle.net/11370/79cf5e84-62ff-456d-8fc3-2174969cd1b9 https://research.rug.nl/en/publications/79cf5e84-62ff-456d-8fc3-2174969cd1b9 https://doi.org/10.5253/078.098.0204 https://pure.rug.nl/ws/files/2614121/2010ArdeaKraan.pdf |
Summary: | 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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