Scientists fear seabird die-off as El Niño looms: ‘We don’t know how bad this is will get’ | San Diego

Marine ornithologist Tammy Russell found the furry carcasses, one after another, within minutes of walking along the San Diego beach.

Some were mixed with washed moss. Others were under rocks.

Every month, scientists and volunteers conduct surveys of dead seabirds and find what Russell describes as a grim assessment of the impact of a massive months-long marine heatwave on parts of the California coast.

Research conducted by various organizations over decades helps establish a baseline of knowledge about coastal marine life to identify threats and their impacts.

Russell, a postdoctoral researcher at the Scripps Institution of Oceanography at the University of California, San Diego, said many seabirds, including California brown pelicans, loons and grebes, have starved to death in recent months as record-breaking ocean temperatures reduced the band of cold, nutrient-rich surface water where krill, anchovies and sardines thrive near shore.

“We’re seeing cormorants walk to shore and die within an hour. So one time it happened within 15 minutes and I’ve never seen that before,” Russell said. “This has been very upsetting to me and we see this happening all along the coast.”

Scientists fear the deaths could be worsened by the recent occurrence of El Niño, a natural warming of parts of the Central Pacific that is changing weather patterns around the world and raising global temperatures.

In June, the US National Oceanic and Atmospheric Administration confirmed that El Niño was occurring, and it is expected to reach historic strength.

Seabird deaths occur periodically, and not all seabird deaths off California this year were tied to a marine heat wave, scientists and wildlife officials say.

But as the planet warms and the oceans warm, such deaths are becoming more frequent.

‘We don’t know how bad this will be’

A marine heatwave has persisted along parts of the west coast throughout the past year, marking the third time on record that so much of coastal waters have remained warm for so long, according to Noaa.

Scripps measures daily ocean temperatures at 10 coastal stations along the California coast and says its records go back more than a century. This year, three stations set records for 40 days or more, said Melissa Carter, the program’s director. Samples are collected in a variety of ways, including dropping an insulated bucket off a pier or by lifeguards in the early morning surf or by researchers on rocky shorelines.

Robotic underwater gliders with sea-operated sensors also recorded high temperatures offshore and at depth during spring. The warm temperature anomaly in Southern California this spring is comparable to that of the last El Niño in 2023, said Dan Rudnick, who runs the Scripps glider program.

And that was before the formation of this year’s El Niño, which could extend into 2027.

As cold-water species move deeper and northward, the marine heat wave combined with El Niño could further disrupt the food webs of marine life, from gray whales to seabirds. A similar pattern occurred ten years ago.

“We don’t know how bad this is going to get,” said Russell, who has written about the five Booby species now common off California as ocean temperatures rise.

Seabirds look for food in unusual places

Wildlife rehabilitation facilities treated hundreds of emaciated birds this spring as a marine heat wave intensified.

“It’s not unusual to see dead birds on the beach, but the amount of dead birds is unusual,” J.D. Bergeron, CEO of International Bird Rescue, a global wildlife conservation organization that operates two waterfowl rehabilitation centers in California, said in a May interview.

Brown pelicans are showing up in inland lakes, Bergeron said.

“When birds, especially pelicans, are starving, they start looking in unusual places for food,” he said. “They will chase fishing boats, go to piers, and you will end up with birds injured by fishing lines and fishing hooks.”

Most of the dead or emaciated seabirds examined this year were young and emaciated, and most tested negative for bird flu, according to the California Department of Fish and Wildlife. Some had opportunistic infections linked to malnutrition.

Senior state environmental scientist Krysta Rogers said there may be factors besides warm ocean temperatures. High mortality rates among young Brandt’s cormorants and common murres began after a strong breeding season in 2025, reaching a post-winter peak and appearing to coincide with a marine heatwave. These deaths can often be caused by the chicks not being able to survive on their own, he said.

But he is not ruling out a marine heatwave affecting some seabirds, as he thinks there has been an increase in reported deaths this spring, not just from juveniles but from other species as well.

The U.S. Fish and Wildlife Service, which collects data from dead seabird surveys and others, said a comprehensive report was not yet ready.

Only a small fraction of birds killed at sea wash up on shore

In 2013, a mass of warm water nicknamed the “blob” developed off the coast of Alaska and persisted for years, extending southward to Mexico’s Baja California peninsula, damaging marine ecosystems. One of the strongest El Niños on record coincided with it in 2015.

Emaciated carcasses of common murres have turned up on beaches in what biologists say is the largest recorded seabird die-off in the world’s oceans.

Rampant murders look like weak penguins. They can fly for miles to find schools of finger-long fish and dive and swim to depths of about 183 meters to catch them. However, birds’ high metabolism means they need to eat a lot. If they do not eat prey worth 10% to 30% of their body mass on a daily basis, they can deplete their fat reserves and fall to a critical starvation threshold within three days.

Research shows that only a small fraction of birds that die at sea wash up on shore. It took years for scientists to confirm that more than half of Alaska’s common murre population, an estimated 4 million birds, died during the “drop,” according to a 2024 study in the journal Science.

The species is still struggling to recover.