Marine heatwaves off the coast of North America cause huge seabird die-offs, according to a study
The research, published in Marine Ecology Progress Series, draws on data from four citizen science projects (COASST, BeachCOMBERS, Beach Watch and the British Columbia Beached Bird Survey) to examine coastal birds from central California to Alaska, between 1993 and 2021.
Dead Tufted Puffins found in October 2016 (Aleut Community of St Paul Island Ecosystem Conservation Office).
In total, the researchers collated 90,000 surveys of 106 seabird species on more than 1,000 beaches. "This is truly a global dataset that asked a global-sized question: Does a warming world significantly impact marine birds, among the top predators in the nearshore marine environment?" says paper co-author Julia Parrish, a professor of aquatic and fishery sciences at the University of Washington.
"We find a dramatic delayed effect. A warmer ocean, and certainly a suddenly warmer ocean as happens during an El Niño or a marine heatwave, will result in the death of hundreds of thousands to millions of marine birds within one to six months of the temperature increase," she added.
They found a stark connection between marine heatwaves and seabird die-offs in the last three decades. Of particular note was five events between 2014 and 2019, each of which had at least a quarter of a million bird deaths.
The precise cause of each die-off is different, but all are warming-related, according to the researchers: things like harmful algal blooms, disease spread, and changes in the food available.
Reference
Jones, T, Parrish, J K, Lindsey, J K, Wright, C, et al. 2023. Marine bird mass mortality events as an indicator of the impacts of ocean warming. Mar Ecol Prog Ser. DOI: https://doi.org/10.3354/meps14330
