Washington coast avian flu outbreak devastated Caspian terns, jumped to seals
An epidemiological study found that 56% of a large breeding colony of Caspian terns died from a 2023 outbreak of highly pathogenic avian influenza at Rat Island in Washington state. Since then, no birds have successfully ...
As part of the study, a team including Washington Department of Fish and Wildlife (WDFW) as well as Washington State University researchers also documented that the avian flu virus H5N1was transmitted to harbor seals for the first time in the northeastern Pacific.
While there has not been another large coastal wildlife outbreak of H5N1 since, researchers estimated that about 10%–14% of the Caspian tern population in the Pacific flyway have been lost to H5N1 infections.
"This Caspian tern event was the first big marine environment avian flu outbreak for Washington. It caused a significant, punctuated mortality for the Caspian terns, which were already a species in decline throughout this flyway," said Katherine Haman, a wildlife veterinarian for WDFW and lead author on the study published in the journal Frontiers in Veterinary Science.
Caspian terns are found across the country, and until a couple years ago, their largest breeding site was an island in the lower Columbia River, downstream from Portland. Because the birds were feasting on young, endangered salmon, they were discouraged from nesting on that island. It is likely that a portion of the extremely large Columbia River colony relocated to Rat Island near Fort Flagler Park in Jefferson County—then, came the avian flu in 2023.
Haman credited citizen volunteer docents from the Friends of Fort Flagler and local kayaking guides with noticing the first bird deaths on Rat Island early and alerting officials. This allowed researchers to respond early, collecting dead birds and euthanizing sick ones. A total of 1,101 adults and 520 chicks were killed by the outbreak.
The avian flu killed 1,101 adult Caspian terns and 520 chicks in 2023 in a large breeding colony on Rat Island in Washington state. Researchers estimate that as much as 10%–14% of terns in the entire Pacific flyway have been lost to the virus. Credit: Scott Pearson, Washington Department of Fish & Wildlife
The population of Caspian terns were already in decline throughout the Pacific flyway when they suffered a major avian flu outbreak at a large breeding site off the coast of Washington state. Credit: Scott Pearson, Washington Department of Fish & Wildlife
Researchers were able to respond early to the outbreak of avian flu among Caspian terns in 2023, thanks to the reports from local volunteers and kayaking guides. The event was the first major outbreak of H5N1 among marine wildlife in the region. An estimated 56% of the breeding colony was lost. Credit: Katherine Haman, Washington Department of Fish & Wildlife