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...

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Bibliographic Details
Published in:Ardea
Main Authors: Kraan, Casper, van Gils, Jan A., Spaans, Bernard, Dekinga, Anne, Piersma, Theunis
Format: Article in Journal/Newspaper
Language:English
Published: 2010
Subjects:
connectivity
East-Atlantic Flyway
foraging
habitat suitability
macrozoobenthos
migration
molluscivore shorebirds
predicted intake rate
AFFECTS FORAGING DECISIONS
COST-BENEFIT-ANALYSIS
INTERTIDAL FLATS
PATCH-CHOICE
ORGAN SIZE
FOOD
SHOREBIRD
BEHAVIOR
WADERS
LENGTH
Calidris canutus
Taimyr
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
Description
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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