The Tricolored Blackbird has one of the most restricted ranges of any North American bird, with 95% of it’s breeding population in the Sacramento and San Juaquin Valleys of California. Only a few scattered breeding sites exist outside the Central Valley in Southern California and southern Oregon, and single sites in Washington, Nevada, and extreme northwestern Baja California. Like other blackbirds, it is a highly gregarious species, forming massive breeding colonies (up to 200,000 nests reported in one colony) and huge winter roosts that spread out to forage over a large area by day. This Red Watch List species has declined precipitously in recent decades, due primarily to a shift in nesting behavior that has put the species in direct conflict with current farming practices.
Historically, Tricolored Blackbirds nested throughout the Central Valley in freshwater marshes dominated by cattails and bulrushes, and in adjacent riparian willows. With loss of wetlands, more and more colonies shifted to agricultural fields, and this trend has been exacerbated recently by the long-term drought in California. Many recent colonies are associated with dairy farms and feedlots, and especially fields of triticale—a hybrid wheat-rye grain grown as forage for cows. These colonies are highly vulnerable, as fields may be harvested while young blackbirds are still in the nests, resulting in nearly total reproductive failure. A partnership of federal, state, and private landowners is working on solutions, including incentives for farmers to delay harvest, in an effort to keep this species from becoming endangered.
Primary Habitats:Wetland - freshwater marsh; agricultural
Agricultural Conversion, Climate Change
Population Loss Since 1970: >50%
Urgency/Half Life: unknown
Global Conservation Status: IUCN 2016-3 Red List – Endangered
U.S. Conservation Status: Petitioned for ESA listing (decision pending)
Canadian Conservation Status: N/A
Birds of Conservation Concern: USFWS – Bird of Conservation Concern; BLM – Sensitive Species
|Region||Area Importance||Long-term population change||Half life|
|Central Valley Joint Venture||50%||-61%||***|
|Sonoran Joint Venture||20%||-61%||***|
|San Francisco Bay Joint Venture||7%||-61%||***|
*** indicates insufficient or unreliable data to calculate a half-life estimate.
Tricolored Blackbird Portal to Working Group
- Better understanding of precise locations and habitats used by Tricolored Blackbirds, especially in winter
Species Conservation Plans:
- The Bureau of Land Management designates the Tricolored Blackbird a Sensitive Species (BLM 2003).
- Hamilton 2004. California Partners in Flight Riparian Bird Conservation Plan – Tricolored Blackbird (Agelaius tricolor)
Key Species References:
Peer Reviewed Papers:
Holyoak et al. 2014. Combining site occupancy, breeding population sizes and reproductive success to calculate time-averaged reproductive output of different habitat types: an application to Tricolored Blackbirds
Graves et al. 2013. Understanding the contribution of habitats and regional variation to long-term population trends in tricolored blackbirds
Meese 2012. Cattle egret predation causing reproductive failures of nesting tricolored blackbirds
Meese and Simmons 2010. Safe and effective methods for trapping and color banding tricolored blackbirds in the Central Valley of California
Meadows 2008. Cooperative conservation could save tricolored blackbirds
Shuford and Gardali (editors) 2008. California Bird Species of Special Concern: A ranked assessment of species, subspecies, and distinct population of birds of immediate conservation concern in California.
Cook and Toft 2005. Dynamics of extinction: population decline in the colonially nesting Tricolored Blackbird Agelaius tricolor
Birds of North America (BNA) Species Account