Nearly all of the world’s tricolored blackbirds nest in the Central Valley and nearby foothills. Yolo County has been home to several breeding colonies in recent years, totaling twenty thousand or so adults, and often with large numbers in winter as well. Thus, Yolo Audubon has an unusually direct stake in the welfare of the species.
Through the mid-twentieth century, tricolors nested mainly in tule marshes and foraged in nearby grassland. With the marshes and grassland mostly gone, the larger colonies nowadays are in grain fields near dairies in the San Joaquin Valley, with smaller ones in blackberry thickets and other thorny plants, mainly on cattle grazing land in the Sierra foothills. Both the individual colonies and the overall population are much smaller than they once were, and the species is listed as threatened by the California Department of Fish and Wildlife (CDFW).
Reliance on landscapes managed for cattle is often problematic for the birds. Because grain fields are normally harvested a week or two earlier than tricolors finish nesting, the harvest can destroy much of a season’s production of fledglings. To prevent this, Audubon California, the Natural Resources Conservation Service, CDFW, and the US Fish and Wildlife Service, in various combinations, have worked with growers since 2015 to delay or forego harvest. This has succeeded, but relies every year on the cooperation of growers and on having money to compensate them.
Until now, the federal government has reimbursed farmers about 75% of the economic losses incurred by delaying harvest. This year, and for the next two years, that amount is down to 50%, and the partners are scrambling to make up the difference. Audubon California has taken the unusual step of asking local chapters to pledge funds to close the gap, if other sources prove insufficient. It doesn’t get much more precarious than that.
With all the money spent, how effective is the intervention? The decline in tricolor numbers probably has stopped, but neither is there a clear sign of rebound. Nesting colonies move around from year to year, making it hard to find and count the birds, and colonies continue to be destroyed, inadvertently or otherwise.
The fate of tricolor colonies in Yolo County is typical in its inconsistency. The largest known colony, with fifteen or twenty thousand adults, is in a cattail marsh on Conaway Ranch along Road 25. It is carefully managed and has persisted for years. About four other colony sites have been found recently on the east edge of Woodland, mostly in thistle patches. The one at North Regional Pond fledged a thousand or more young last year, but colonies have twice been destroyed by mowing machines, and one was cleared of vegetation after one year of use.
Everyone involved recognizes the need for more durable solutions. The birds need more nesting sites free of land use conflicts. Audubon California is looking for help from private wetland owners in the San Joaquin Valley. Here in Yolo County, a plan is in preparation for improvements at North Regional Pond. Stay tuned.
Michael Perrone, YAS Conservation Chair