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

TY - JOUR

T1 - Connecting foraging and roosting areas reveals how food stocks explain shorebird numbers

AU - Bakker, Wiene

AU - Ens, Bruno J.

AU - Dokter, Adriaan

AU - van der Kolk, Henk Jan

AU - Rappoldt, Kees

AU - van de Pol, Martijn

AU - Troost, Karin

AU - van der Veer, Henk W.

AU - Bijleveld, Allert I.

AU - van der Meer, Jaap

AU - Oosterbeek, Kees

AU - Jongejans, Eelke

AU - Allen, Andrew M.

N1 - 7279, AnE; Data archiving: data archived at publisher (not NIOO data)

PY - 2021/9/30

Y1 - 2021/9/30

N2 - 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.

AB - 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.

KW - Connectivity

KW - Europe

KW - Foraging behaviour

KW - Local movements

KW - Netherlands

KW - Oystercatcher

KW - Population size

KW - Wadden sea

KW - Zoobenthos

KW - international

KW - Plan_S-Compliant-TA

U2 - 10.1016/j.ecss.2021.107458

DO - 10.1016/j.ecss.2021.107458

M3 - Article

AN - SCOPUS:85107745887

SN - 0272-7714

VL - 259

JO - Estuarine, Coastal and Shelf Science

JF - Estuarine, Coastal and Shelf Science

M1 - 107458

ER -