Key facts
- A marine heat wave has caused a significant die-off of seabirds along the California coast.
- Record ocean temperatures have depleted the food supply of krill, anchovies, and sardines.
- Scientists fear the situation will worsen with the formation of a potentially historic El Niño.
- Wildlife rehabilitation centers have treated hundreds of emaciated birds.
- Many dead seabirds tested negative for avian flu, indicating starvation as a primary cause.
- A similar event in 2013, linked to 'the blob' and El Niño, caused a massive die-off of common murres.
Scientists are increasingly concerned about a severe die-off of seabirds along the California coast, a situation they fear could be significantly worsened by the newly formed El Niño. A persistent marine heat wave has already depleted the ocean's surface waters of cold, nutrient-rich areas where essential prey like krill, anchovies, and sardines thrive.
Marine ornithologist Tammy Russell described finding numerous dead seabirds, including California brown pelicans, loons, and grebes, on San Diego beaches. She noted instances of cormorants dying within an hour of reaching shore, a phenomenon she has never witnessed before. These birds are starving due to the scarcity of their usual food sources.
The US National Oceanic and Atmospheric Administration confirmed the formation of El Niño in June, with expectations that it will grow to historic strength. While seabird die-offs are not uncommon, scientists note they are becoming more frequent as global temperatures rise and oceans continue to warm. The current marine heat wave has persisted for over a year, marking only the third time on record for such a prolonged period of elevated temperatures off the west coast.
Researchers at the Scripps Institution of Oceanography have recorded record-breaking ocean temperatures at multiple coastal stations. Robotic underwater gliders have also detected significant warm temperature anomalies offshore. These conditions, coupled with the developing El Niño, could further disrupt marine food webs, affecting species from gray whales to seabirds, a pattern similar to one observed a decade ago.
Wildlife rehabilitation centers have treated hundreds of emaciated birds, with organizations like International Bird Rescue reporting an unusual quantity of dead birds. Brown pelicans have been found in inland areas, desperately seeking food and often sustaining injuries from fishing gear. Most examined birds were young, emaciated, and tested negative for avian flu, pointing to starvation as the primary cause, though some opportunistic infections linked to malnourishment were also noted.
While some mortality, particularly among young seabirds like Brandt's cormorants and common murres, may be linked to post-breeding season survival challenges, scientists acknowledge the marine heat wave's impact on other species. A significant die-off of common murres in 2013, associated with a warm water mass nicknamed 'the blob' and a strong El Niño, resulted in an estimated 4 million bird deaths and has taken years for the population to begin recovering.