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| Tricolored Blackbird [photo by Bill Haas] |
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Title: The Triennial Tricolored Blackbird Survey, Edition 2025
Presenter: Presented by Bill Haas, SLO County Coordinator for the Statewide TRBL Survey
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Description:
The Tricolored Blackbird is insect-dependent during the breeding season and largely granivorous when not breeding. Breeding-season insectivory and non-breeding granivory in this colonial species (colonies of which historically numbered in the 100,000s) put severe constraints on a bird species living in anthropogenic landscapes, where both insects and blackbirds are typically considered pests. For example, following the breeding season, most Tricolored Blackbirds move into the Sacramento Valley (although "ours" typically disperse locally), where they feed on ripening rice with other blackbirds (Beedy et. al. 2020).
Due to their similarity in appearance to Red−winged Blackbirds, which may be legally taken (killed) without a permit under a depredation order (50 CFR 21.43), many Tricolored Blackbirds are shot each fall as they feed on ripening rice. This, in addition to historical conversion of Central Valley marsh to agriculture (and other factors) have caused the Tricolored Blackbird population to drop substantially since the 1930s. Surveys in 1934 estimated >700,000 birds in just eight counties (Neff 1937). In contrast, surveys in 2014 estimated 145,000 birds in 37 counties (Meese 2014).
Since 1994, the statewide survey has been the primary means by which the population of this species is assessed. The goal of the survey is to obtain a statewide estimate of the number of adult Tricolored Blackbirds in California. Tricolored Blackbirds are most accurately and comprehensively counted when at their breeding colonies; they are relatively sedentary at breeding colonies, when most of the population(s) congregate, which allows observers to make multiple, statistically significant estimates of colony size. (References available on request.)
Bill Haas will present a brief history of the survey; an assessment of the current status of the species statewide and locally; a brief description of the survey protocol; an introduction to a program he has initiated with the State, California, Audubon, and several resource conservation districts to create or restore breeding habitat in SLO, Monterey, and Santa Barbara counties.
Bio: Bill’s initial interest in the Tricolored Blackbird dates back to the early 1990s when, having recently returned from a 4-year Peace Corps assignment in Central America, he moved to San Diego. There he met Philip Unitt, the current curator of birds and mammals at the San Diego Natural History Museum. Phil’s interest in San Diego County’s breeding birds was contagious and when Bill asked which county species were of greatest interest to Phil and to the Museum, he responded: “Willow Flycatcher and Tricolored Blackbird.” The result? A 20-year study of the Southwestern Willow Flycatcher along the San Luis Rey River and an annual assessment of “Trikes” wherever he moved, which, after San Diego included Butte, Tehama, Glenn counties and currently, Kern, Monterey, and San Luis Obispo Counties. He is currently the State’s triennial survey coordinator for San Luis Obispo County. The 2025 survey will be Bill’s 8th, and 4th as a county coordinator.
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