Connecting foraging and roosting areas reveals how food stocks explain shorebird numbers

Bakker, Wiene, Ens, Bruno J., Dokter, Adriaan, van der Kolk, Henk Jan, Rappoldt, Kees, van de Pol, Martijn, Troost, Karin, van der Veer, Henk W., Bijleveld, Allert I., van der Meer, Jaap, Oosterbeek, Kees, Jongejans, Eelke, and Allen, Andrew M. (2021) Connecting foraging and roosting areas reveals how food stocks explain shorebird numbers. Estuarine, Coastal and Shelf Science, 259. 107458.

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Abstract

Shorebird populations, especially those feeding on shellfish, have strongly declined in recent decades and identifying the drivers of these declines is important for conservation. Changing food stocks are thought to be a key driver of these declines and may also explain why trends have not been uniform across Europe's largest estuary. We therefore investigated how winter population trends of Eurasian oystercatchers (Haematopus ostralegus) were linked to food availability in the Dutch Wadden Sea. Our analysis incorporated two spatial scales, a smaller scale focused on roost counting areas and food available to birds in these areas and a larger spatial scale of tidal basins. A novelty in our study is that we quantify the connectivity between roosting and foraging areas, identified from GPS tracking data. This allowed us to estimate food available to roosting birds and thus how food availability may explain local population trends. At the smaller spatial scale of roost counting areas, there was no clear relationship between available food and the number of roosting oystercatchers, indicating that other factors may drive population fluctuations at finer spatial scales. At the scale of tidal basins, however, there was a significant relationship between population trends and available food, especially cockle Cerastoderma edule,. Mortality and recruitment alone could not account for the large fluctuations in bird counts, suggesting that the site choice of wintering migratory oystercatchers may primarily drive these large fluctuations. Furthermore, the relationship between oystercatcher abundance and benthic food stocks, suggests winter shorebird counts could act as ecological indicators of ecosystem health, informing about the winter status of food stocks at a spatial scale of tidal basins.

Item ID: 69615
Item Type: Article (Research - C1)
ISSN: 1096-0015
Keywords: Connectivity, Europe, Foraging behaviour, Local movements, Netherlands, Oystercatcher, Population size, Wadden sea, Zoobenthos
Copyright Information: © 2021 The Authors. Published by Elsevier Ltd. This is an open access article under the CC BY license (http://creativecommons.org/licenses/by/4.0/)
Date Deposited: 14 Oct 2021 00:16
FoR Codes: 31 BIOLOGICAL SCIENCES > 3103 Ecology > 310307 Population ecology @ 100%
SEO Codes: 18 ENVIRONMENTAL MANAGEMENT > 1802 Coastal and estuarine systems and management > 180201 Assessment and management of coastal and estuarine ecosystems @ 100%
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