Scientists Fear More Seabirds Will Die as Ocean Temperatures Rise

Hundreds of seabirds are dying along California's coast, and scientists are worried things could get even worse. A marine heat wave — a long stretch of unusually warm ocean water — has been sitting off the California coast for more than a year. The warm water is pushing fish deeper and farther away, leaving birds like pelicans, loons, and cormorants with little to eat. Now, scientists say a weather pattern called El Niño could add to the problem.

Marine ornithologist Tammy Russell studies seabirds at the University of California, San Diego. She walks beaches in San Diego each month to count dead birds washed ashore. In just a few minutes on one recent visit, she found one feathered body after another — some tangled in kelp, others tucked under rocks. 'We've been seeing cormorants walk to shore and then just die within the hour,' she said. 'That has been heartbreaking for me, and we're seeing this happening across the whole coast.'

Scientists and volunteers have been doing these beach surveys for decades. The counts help build a picture of how healthy ocean life is over time. When the numbers of dead birds spike, it is a warning sign that something is wrong in the ocean. This year, the numbers have been alarming.

The marine heat wave has pushed cold, nutrient-rich water away from the surface near shore. That cold water is where tiny animals like krill live, and where fish like anchovies and sardines feed. Without those fish near the surface, seabirds cannot find enough food. Many birds, especially young ones, have starved to death.

Wildlife rescue centers treated hundreds of very thin, weak birds this spring. JD Bergeron leads International Bird Rescue, a group that runs two bird care centers in California. 'It's not abnormal to see dead birds on the beach, but the quantity of dead birds is unusual,' he said. Brown pelicans have even been spotted at inland lakes, far from the ocean, because they are so desperate for food. Some birds following fishing boats have ended up hurt by fishing lines and hooks.

Scientists at Scripps Institution of Oceanography track ocean temperatures at ten stations along the California coast every day. Their records go back more than one hundred years. This year, three of those stations broke temperature records for forty days or more. Underwater robots with sensors also recorded high temperatures both at the surface and deep below.

Now scientists are watching a new threat closely. El Niño is a natural warming of parts of the Pacific Ocean that changes weather around the world. The US weather agency NOAA confirmed in June that an El Niño has formed and could grow to be one of the strongest on record. It could last until 2027.

A similar warm water event, called 'the blob,' hit Alaska in 2013 and overlapped with a strong El Niño in 2015. That combination caused what scientists believe was the largest seabird die-off ever recorded in the world's oceans. Millions of common murres — birds that look like small penguins — washed up dead on beaches. A 2024 study found that more than half of Alaska's common murre population, about four million birds, died during that event. The species is still trying to recover today.

Common murres show just how hard it is for seabirds to survive without enough food. These birds can fly long distances and dive nearly 600 feet underwater to catch fish. But they have very fast bodies that burn through energy quickly. If a murre does not eat enough fish each day — between 10% and 30% of its own body weight — it can starve within just three days.

State scientists have noted that most of the dead and sick birds this year have been young and very thin. Most have tested negative for bird flu, so disease does not appear to be the main cause. Some had infections that come with being malnourished. California scientist Krysta Rogers said some deaths among young cormorants may be partly because young birds struggle to survive on their own. But she agrees the marine heat wave is playing a role, especially since deaths have also risen among adult birds of other species this spring.