Shortage of cockles in Wadden Sea is affecting migratory birds

Photo: Mark Plomp Stichting Natuurbeelden via Wikimedia Commons
Photo: Mark Plomp Stichting Natuurbeelden via Wikimedia Commons

The hot weather is causing cockles in the Wadden Sea to die off in huge numbers, further endangering the survival of birds that depend on them for food, experts have said.

It’s not the first time the cockle population has been decimated by high temperatures. Similar trends were seen in the hot summers of 2018 and 2019.

The scene – young dead cockles littering the beach at the small island of Griend and fewer, older and bigger ones on the shores of Ameland and Schiermonnikoog – is reminiscent of the 2018 drought, marine researcher Roeland Bom told local broadcaster Omrop Fryslân.

‘We saw exactly the same thing very soon after the very hot weather we had then,’ he told the broadcaster.

Bom and his colleagues from the institute for marine research NIOZ are currently investigating tidal flats in the Wadden Sea and the effects of climate change on birds and their food sources.

They think the cockles die at low tide when the sun is at its hottest. ‘It is something which we will see more often as summers are getting warmer,’ he said.

Bom said the cockle population will probably survive, but their dwindling numbers may affect migratory birds which rely on cockles to stock up on energy for the journey to their breeding grounds.

Other bivalves, such as the baltic tellin, are still around in sufficient numbers to serve as an alternative food source but they are much smaller and cost more energy to open, he explained.

‘Red knots, oystercatchers and eider ducks are not doing very well anyway. We think that is because there is not enough food around. This will probably make it worse but more investigation will be needed,’ Bom said.

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