Updated 18 May 2026
If you live in the Southern part of COASST “territory” (Northern California and Southern Oregon), you may have noticed more beached Common Murres, Brandt’s Cormorants, and Brown Pelicans than usual these past few months. This trend initially showed up further South in our sister program’s “territories” (BeachWatch and BeachCombers). In early March, BeachWatch sent out an alert that a mortality event might be underway and all the dead and injured bird organizations quickly got together to share data and make sure the event was documented. Thank you to the hardworking COASST volunteers who collect that data!
Initially, scientists were concerned that this might be tied to Highly Pathogenic Avian Influenza (HPAI), but tests have come back negative. Many of the birds documented by the California Department of Fish and Wildlife and their partners have been on the young side, emaciated, and sometimes with additional infections or injuries.1 Essentially, it seems that starvation may be a factor. This event seems to be particularly affecting Common Murres (COMU), Brandt’s Cormorants (BRCO), and Brown Pelicans (BRPE), and may be tied to increasing ocean temperatures in the region, which can affect these bird’s food sources.2
So what have we seen in our COASST regions?
In general, COASSTers have been encountering fewer than expected beached birds since January. However, there is a different story happening at the species level. While the actual numbers of each species found may seem low (they thankfully aren’t in the 100s!), these COMU, BRCO, and BRPE are arriving out of the expected season, and comparison to our baseline encounter rates (how many beached birds is normal to see) reflect that!
We saw elevated numbers of COMU in Mendocino and Humboldt in January (~ 3 times the usual baseline we would expect), followed by a similar spike in southern Oregon in February before all regions returned to normal.
Few BRPE have been seen by California COASSTers, but their encounter rate in Oregon was 9 times the expected baseline (both in Southern and Northern Regions) in April.
Encounter rates of BRCO in the Mendocino region climbed from twice the expected baseline in January, to 9 times the expected baseline in April. Humboldt saw increased encounter rates through February and March, reaching 6 times the expected baseline in April. Oregon has been more variable but also saw a spike in April (9 times baseline in Southern Oregon, 3 times baseline in Northern Oregon).
While we hope the event will wind down soon, we are continuing to monitor and share data with our partners. Thank you to all our COASSTers helping us keep watch on the coast!
References