Marine ornithologist Tammy Russell walks along a San Diego beach and within minutes finds them: dead seabirds scattered among kelp and wedged under rocks. Brown pelicans, loons, grebes, cormorants. Some so weak they wash ashore and collapse within an hour.
The bodies tell a story of ecological crisis unfolding along the California coast. Record ocean temperatures have crushed the cold, nutrient-rich waters where krill, anchovies and sardines cluster near shore. Without food, seabirds are starving to death in unprecedented numbers this year.
"We've been seeing cormorants walk to shore and then just die within the hour. One time it happened within 15 minutes, and I've never seen that before," Russell, a postdoctoral scholar at UC San Diego's Scripps Institution of Oceanography, said. "That has been heartbreaking for me and we're seeing this happening across the whole coast."
The crisis may worsen. The National Oceanic and Atmospheric Administration confirmed in June that El Niño has formed and is expected to reach historic strength, potentially lasting into 2027. The natural warming pattern of central Pacific waters alters weather worldwide and spikes global temperatures, conditions that compound the existing marine heat wave grinding through California's coastal ecosystem.
Russell articulated the fear gripping scientists: "We don't know how bad this is going to get."
The marine heat wave off parts of the west coast has persisted for the past year, marking only the third time on record that such a large section of coastal waters stayed warm for so long, according to NOAA. At Scripps' 10 temperature monitoring stations stretched along the California coast, where records extend over a century, three stations this year broke records for 40 days or more, according to Melissa Carter, the program director.
Robotic underwater gliders with sensors recorded comparable warm anomalies offshore and at depth during spring, similar to conditions during the last El Niño in 2023. Researchers worry that as cold-water species move deeper and farther north, the combined pressure of heat wave and El Niño could demolish food webs affecting everything from gray whales to seabirds.
A decade ago, a similar pattern triggered catastrophic consequences. In 2013, a warm water mass nicknamed "the blob" developed off Alaska and stretched south, lingering for years. When it overlapped with one of the strongest El Niños on record in 2015, the result was the largest seabird die-off recorded in the world's oceans. Common murres, thin penguin-like birds that can dive nearly 600 feet to hunt finger-length fish, washed ashore emaciated by the thousands.
The die-off was so massive it took years to confirm what happened. A 2024 study in the journal Science found that more than half of Alaska's common murre population, an estimated 4 million birds, perished during the blob. The species is still struggling to recover.
Wildlife rehabilitation facilities treated hundreds of emaciated birds this spring when California's marine heat wave intensified. JD Bergeron, CEO of International Bird Rescue, which runs two aquatic bird rehabilitation centers in California, said the volume of casualties stands out. "It's not abnormal to see dead birds on the beach, but the quantity of dead birds is unusual," he said.
Starving seabirds exhibit desperation. Brown pelicans are turning up in inland lakes searching for food in unsuitable habitats. Bergeron described the behavior: "When birds starve, especially the pelicans, they start to look in unusual places for food. They will chase fishing boats, they will go to piers and you end up with birds with fishing line and fish hook injuries."
Many of the dead and debilitated seabirds examined this year have been young and severely malnourished, and most tested negative for avian flu, according to the California Department of Fish and Wildlife. Some showed opportunistic infections linked to starvation. Krysta Rogers, a senior state environmental scientist, noted that high mortality among young Brandt's cormorants and common murres began after a robust breeding season, peaking post-winter, and appeared to coincide with the marine heat wave. Those particular deaths may stem partly from chicks simply not surviving on their own.
But the broader pattern troubles officials. An increase in reported deaths this spring extended to multiple species and age groups, suggesting the marine heat wave is taking a wider toll.
The truly grim mathematics: only a fraction of birds that die at sea wash ashore. Scientists likely never know the full scope of the catastrophe. If the past is prologue, the visible carcasses represent a fraction of the actual die-off unfolding beneath the surface.
Author James Rodriguez: "When a decade-old disaster already killed 4 million birds and those survivors haven't recovered, a stronger El Niño on top of a lingering heat wave isn't a forecast, it's a sentence."
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