In spring, Tricolored Blackbirds stage one in every of California’s nice birding spectacles, amassing within the tens of hundreds to breed within the Central Valley. This season, the most important colony documented thus far is in Merced County, with a preliminary estimate of 29,000 birds. Like many chook species, these charismatic blackbirds are extensively studied and monitored in the course of the breeding season—in spite of everything, that is when they’re most obvious throughout the panorama. Much less is thought about their lives throughout the remainder of the yr, once they disperse throughout the state and mingle with their extra frequent cousins, just like the Pink-winged Blackbird. Insights from full annual-cycle monitoring can increase our understanding and assist information conservation decision-making.
Defending Colonies Takes Collaboration and Cautious Timing
Throughout the breeding season, we discover tricolored blackbirds nesting in an array of habitats—upland grasslands, wetlands, and fallow fields. Many colonies, nevertheless, type in grain fields adjoining to dairies, partly as a result of California has misplaced greater than 90% of its historic wetland habitat, leaving fewer pure breeding websites throughout the panorama. As a result of these working lands are managed on tight seasonal timelines, nesting can create actual challenges for each birds and producers.
Audubon has labored alongside companions at Pure Assets Conservation Service (NRCS), California Departments of Fish and Wildlife (CDFW), and the dairy business to develop sensible, collaborative options. Via focused outreach and conservation incentives, we’ve protected the overwhelming majority of colonies annually whereas minimizing monetary impacts on dairy operators.
The success of our program has translated into an encouraging rebound within the inhabitants, up 58% between 2014 and 2025. Nonetheless, issues stay concerning the long-term viability of the inhabitants, as agricultural practices and land makes use of change throughout their vary. Water-use restrictions within the face of recurring drought might result in intensive land retirement, which can translate into much less nesting habitat of their core vary. The fast unfold of utility-scale photo voltaic and concrete growth within the Central Valley and its fringes is already decreasing each nesting and foraging habitat.
Advances in Expertise Assist Tricolored Blackbird Actions
Within the face of those questions, there’s a urgent want for extra knowledge on all points of the species’ habitat use. In 2025, Audubon California partnered with the California Division of Fish and Wildlife (CDFW) to tag breeding Tricolored Blackbirds with Mobile Monitoring Applied sciences (CTT) Motus tags to generate novel understandings of their post-breeding and winter lives. We tagged 104 Tricolored Blackbirds and put in our fifth Motus station, complementing an already intensive community throughout California.
Avian monitoring applied sciences are continually advancing. Extremely-lightweight telemetry tags, together with long-lasting battery and solar-powered choices, now make it attainable to trace smaller birds and different wildlife than ever earlier than. On the identical time, strong receiver networks permit for autonomous knowledge assortment throughout broad geographic scales.
A Motus station is basically an array of antennas linked to a pc that passively listens for distinctive coded indicators at a selected radio frequency. When a tagged Tricolored Blackbird flies close by (inside 10 miles sometimes), its CTT Hybrid Tag emits a novel sequence of beeps each few seconds. The station logs these detections and each few days sends the information over the mobile community to Motus, the place it’s compiled in an enormous, shared database.
Between Might 2025 and April 2026, our 130 tagged birds have been detected a million occasions! We’ve seen intensive motion of birds from the higher Sacramento Valley to the southern reaches of the San Joaquin Valley. Moreover, we’ve seen just a few birds depart the Central Valley totally, one to Monterey Bay and one other crossing the Tehachapis heading south.
Tricolored Blackbirds Rely on Grasslands, Too
By late September 2025, 30 of the 104 Tricolored Blackbirds tagged on the time have been detected at a single station in Solano County. We had constructed this station at Calhoun Reduce Ecological Reserve as a result of eBird Standing and Traits predictions indicated the world was a significant hotspot for post-breeding Tricolored Blackbirds. Positive sufficient, the Motus detections confirmed {that a} substantial variety of people had congregated on this area, characterised by rolling hills of grazing land and irrigated pastures.
Although we regularly consider Tricolored Blackbirds as being related to wetlands and dairies, this statement highlights the significance of grasslands to the birds’ habitat necessities.
Grasslands, amongst California’s most imperiled ecosystems with solely round 1% of their historic vary remaining, present crucial foraging sources for these blackbirds, as they’re wealthy in nutritious invertebrates like grasshoppers. Their nesting colonies are hardly ever distant from pastures or rangelands, and our outcomes point out grassland habitats are additionally wanted within the fall.
Many insights stay unearthed from our Motus examine, and we’re solely starting to scratch the floor of the information. As our tagged birds progress via the 2026 breeding season, we’re persevering with to gather novel details about the place they go after breeding and the way they transfer between areas over the course of the yr.
Already, cross-regional linkages are rising between the Sacramento Valley and the Tulare Basin. Birds that bred in Colusa County final yr have been detected in Kern County this spring, the place we anticipated they might breed in 2026. This Colusa County-to-Kern County connection is important as a result of it reveals that Tricolored Blackbirds could also be shifting between main breeding areas, emphasizing the significance of defending habitat throughout their broader vary, not simply at particular person colony websites.
We’re additionally partnering with different researchers finding out the species in different areas. Ornithologists at Southern Sierra Analysis Station and the San Diego Pure Historical past Museum have their very own allotment of tags to affix to birds breeding of their respective areas.
Collectively, these knowledge will assist unlock a extra cohesive image of the species’ statewide, year-round distribution and habitat use.
This work is strengthened via collaboration with companions throughout the area:
- Fresno Audubon Society helped set up the Motus station at Mendota, then went on to construct their very own tower on the Fresno Zoo, increasing the community’s attain within the Central Valley.
- Southern Sierra Research Station has offered intensive help with Motus installations and can be tagging Tricolored Blackbirds within the Kern River Valley, serving to strengthen our understanding of the species’ actions throughout one other necessary area.
- Point Blue Conservation Science supported the work via contractors who helped with the Mendota Motus station and assisted with some tagging efforts.
- The Nature Conservancy supported tagging efforts within the discipline.
- River Partners put in extra Motus towers within the area, which can assist enhance the possibilities of detecting tagged Tricolored Blackbirds as they transfer throughout the panorama.
Taken with future alternatives to become involved?
If you happen to’d wish to study extra about becoming a member of the following Tricolored Blackbird Triennial Survey in 2028, electronic mail Ian Souza-Cole at ian.souzacole@audubon.org.
