When the Ocean Gets Too Warm, Birds Go Hungry

For many, the Brown Pelican is a welcome sight on a beach visit – a sign of the warm sand and sun. They can be seen across this hemisphere’s coastlines but are most prevalent in those warmer, vacation destinations. Here on the Pacific coast of the United States, the California subspecies of the Brown Pelican (pelecanus occidentalis californicus) is a regular fixture along our beaches. That association with warm places may be misleading, though. What the pelican actually depends on is cold water, or rather, food that depends on cold water. California Brown Pelicans feed heavily on northern anchovy, and they follow anchovy movements year-round. Anchovy, in turn, depend on the cold, nutrient-rich upwelling of the California Current, which fuels the plankton blooms at the base of that food web. When that upwelling weakens or surface waters warm, the anchovy becomes harder to come by and the pelicans go hungry. 

Pelicans aren’t the only species that can feel these effects. Murres, auklets, cormorants, and shearwaters all depend on the same cold-water food web, feeding on forage fish species ranging from Pacific sand lance and herring to krill and copepods. This makes seabirds and marine mammals especially vulnerable to the effects of marine heatwaves. 

Marine heatwaves are discrete events - a stretch of days to months when ocean temperatures at a given location run well above normal for that place and time of year. Warm surface water suppresses the upwelling that brings nutrients up from below, reducing the volume of plankton and the forage fish that feed on it. Marine heatwaves are caused by a combination of factors, including long-term ocean warming, and their occurrence raises the elevated baseline temperature even further, causing higher temperatures and more impacts to the marine food web. And these events have grown both more frequent and more severe in recent decades. 

In fact, we’re currently experiencing an exceptional marine heatwave in the North Pacific. Since last winter, this heatwave has been killing seabirds, with die-offs concentrating in California and places to the south. Ocean temperatures recorded daily at the Scripps Pier in San Diego have run 3 to 7 degrees Fahrenheit above average for months, breaking 38 daily records. This is the highest continuous warm period the station has measured in more than a century. Loons, grebes, cormorants, and, of course, Brown Pelicans have washed ashore emaciated, and local rehabilitation centers have taken in hundreds of starving birds. An even larger die-off is being reported off Ecuador, where surveyors counted more than 1,500 dead seabirds across June and July of this year, which is many times the expected number.  

Though Washington's coasts are currently experiencing normal temperatures, we have not been spared in the past. The 2014–2016 marine heatwave known as "the Blob" stretched from California to Alaska and triggered the largest seabird die-off ever recorded, with roughly four million Common Murres lost among millions of other birds. 

We know this because people were recording the impact. Volunteers with the Coastal Observation and Seabird Survey Team (COASST), based at the University of Washington, survey the same beaches monthly, year after year, and record which birds have washed ashore. That long-term record of baseline conditions is what made it possible to understand the scale of the Blob-induced seabird die-off. 

The current heatwave is not expected to ease anytime soon. For now, Washington's waters are holding - strong seasonal upwelling has kept our sea surface temperatures near normal. And our coasts are even providing habitat for some of the displaced seabirds - researchers are documenting higher numbers of Brown Pelicans along the Washington and Oregon coastlines this summer. Whether these conditions hold through the fall is the open question, and the answer will be measured on our beaches. Data from COASST has been integral to tracking changes in our marine environment, especially the impact of marine heatwaves on birds. And COASST is currently looking for more volunteers on the outer coast of Washington and Oregon, with more details available on the COASST website, along with information on how the data are used and what COASST is currently documenting on coasts from Alaska to California. 

Volunteers can document the impact of marine heatwaves on birds and other wildlife. Preventing future ones is a policy issue. Audubon advocates for natural climate solutions and responsible clean energy siting here and across the country and our Coastal Program leverages this policy work with science and community engagement to protect coastal habitats and the birds that rely on them. This includes the forthcoming Salish Sea State of the Birds, which evaluates available data on how birds are faring in the Salish Sea and identifies where conservation action can address the pressures behind their declines, marine heatwaves among them. 

Policy change depends on decision-makers hearing from constituents, including you. Sign up for Audubon Washington's Action Alerts to weigh in on bird and climate-friendly policies as key opportunities arise throughout the year.