Dead in their nests or washed ashore: why thousands of seabirds are dying en masse

A dead gannet on a beach in Pembrokeshire, Wales. A heatwave in South Africa caused a mass die-off in a colony of Cape gannets that first alerted some ecologists to the effect rising temperatures were having on seabirds. Photograph: Manor Photography/Alamy

Twenty years ago, David Grémillet, a seabird ecologist, watched in dismay as a heatwave hit a breeding colony of Cape gannets in Lambert’s Bay, South Africa, causing dozens of birds to keel over. An unseasonably hot wind sent temperatures to 40C (104F), too intense even for the heat-adapted birds.

While guarding their nests, they baked in the heat, says Grémillet, a researcher at the National Centre for Scientific Research in Montpellier, France. He and his colleague waded into the colony, picking up listless gannets and tossing them into the sea to cool down. Their frantic attempts saved a few, but in just under an hour, 100 birds died.