California Protects Tricolored Blackbird After eBird Data Help Show 34% Decline

They might nest by the thousands in a Central California field one year, then be gone the next. Tricolored Blackbird colonies move unpredictably from year to year, making them notoriously difficult to census. Despite apparent population declines, scientists couldn’t convince California officials that Tricolored Blackbirds needed the state’s protection.

Cornell Lab of Ornithology researcher Orin Robinson and colleagues helped change minds when they developed a new way of estimating population trends for the species using data contributed to eBird by citizen-science participants, as well as from other biological surveys. Their analysis suggests that Tricolored Blackbird experienced a precipitous 34% decline in the past 10 years. These results spurred the State of California to approve state Endangered Species Act protections for Tricolored Blackbirds in April 2018.

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