First DDT, now the flu: Peregrine falcons in San Francisco Bay Area hit hard by H5N1 variant
Highly pathogenic avian influenza (HPAI) featured prominently in the news during 2020 as it took the lives of millions of birds across the globe. While the worst seems to be behind us, population-level effects are just now emerging.
A new study published in the Journal of Raptor Research has revealed a significant decline in nesting peregrine falcons within the San Francisco Bay Area that coincides with an outbreak of the H5N1 highly pathogenic avian influenza. The study, titled "Rapid Decline of Nesting Peregrine Falcons in the San Francisco Bay Region of California Synchronous with an Outbreak of H5N1 Highly Pathogenic Avian Influenza," highlights the crucial role peregrine falcons play as top predators and sensitive indicators of ecosystem health.
The research team, led by Zeka Glucs, director of the Predatory Bird Research Group at the University of California, Santa Cruz, analyzed data from 2000 to 2025 and found that the number of occupied territories for peregrines dropped by 65% within three years of the H5N1 outbreak in California in 2022. The falcons, known for their hunting prowess, are particularly vulnerable to exposure to HPAI through their food sources.
While direct mortality rates are difficult to ascertain due to the birds' elusive nature, researchers emphasize the importance of monitoring sentinel species like peregrine falcons to gauge the severity of the influenza's impact on their population. The findings underscore the need for continued research and public engagement in protecting these birds and other species within the ecosystem.
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