Marine ornithologist Tammy Russell recently made a grim discovery on a San Diego beach. During routine surveys, she found numerous dead seabirds, sometimes tangled in washed-up kelp or hidden under rocks. These findings are part of ongoing research conducted by scientists and volunteers to assess the impact of a prolonged marine heat wave affecting parts of the California coast.
Russell and her team have observed a troubling pattern. Many species, including California brown pelicans, loons, and grebes, have starved due to the warmer ocean temperatures. The heat has reduced the cold, nutrient-rich bands of water near the shore, vital for krill, anchovies, and sardines. These conditions have led to seabirds like cormorants walking ashore and dying within minutes. This alarming trend extends along the entire coastline.
Scientists attribute part of this crisis to the recently developed El Nino event, which warms parts of the central Pacific and impacts global weather patterns. Such die-offs of seabirds are not unprecedented. However, their frequency is increasing as ocean temperatures rise. The U.S. National Oceanic and Atmospheric Administration (NOAA) reports that this is only the third instance on record where such a vast section of coastal waters has remained warm for an extended period.
NOAA’s ongoing temperature monitoring from 10 coastal stations shows record-high readings in three locations for 40 consecutive days this year. Robotic underwater gliders have also documented elevated temperatures offshore and at depth, challenging marine ecosystems.
The continued marine heat wave, coupled with El Nino, poses a risk to cold-water species, prompting them to migrate deeper and further north, disrupting traditional food webs. This disruption impacts a wide range of sea life, including the seabirds struggling to find food.
Wildlife rehabilitation centers have treated hundreds of undernourished birds this spring, with significant numbers appearing along the beaches. J.D. Bergeron, CEO of International Bird Rescue, notes the unusually high number of dead seabirds. He highlights the unusual presence of brown pelicans in inland lakes, suggesting they are desperately seeking food.
Despite testing negative for avian flu, most examined birds were young and emaciated. Some showed opportunistic infections linked to malnutrition. High mortality rates among young birds like Brandt’s cormorants and common murres coincided with the marine heat wave, indicating food scarcity as a significant factor.
In 2013, a warm-water mass known as “the blob” caused widespread marine ecosystem disturbances from Alaska to Mexico, overlapping with one of the strongest El Ninos on record. This event led to the largest seabird die-off recorded in oceanic history.
Most seabirds, such as common murres, rely on daily prey consumption to maintain their high metabolism. When they fail to consume enough, they swiftly reach a critical point of starvation. Studies have shown that only a small percentage of birds that perish at sea eventually wash ashore.
The seabird populations are struggling to recover, with long-term consequences uncertain. The complex interactions between marine heat waves and broader climate phenomena continue to challenge conservation efforts.
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