In recent years California has been home to all of the nesting tricolored blackbirds in the world, and almost all of the breeding birds have been in the Central Valley. This year in Yolo County about 25,000 birds colonized Conaway Ranch at a site north of Road 25 and east of Road 103, and about 10,000 stayed through the nesting period. As at several other places in the Sacramento Valley, the nests were in jungles of tule, cattail, willow and blackberry along canals in and near rice fields. The birds preferred to collect food for their nestlings in rice fields where pesticides are not used, and provided natural pest control by consuming the bugs that eat rice.
This spring brought a concerted effort to find and count the birds statewide. Census-takers estimated about 220,000 birds, which is somewhat more than at the last census five years ago, though with a large margin of error. The big discovery was that distinctly fewer birds were in their traditional stronghold in the southern San Joaquin Valley than in recent decades, and correspondingly more birds were in the lower and middle Sacramento Valley. Some of this may have to do with farmers in Kern County converting grain fields to pistachio orchards, and the recent drought probably diminished the value of dry-land foraging areas.
The drought took a similar toll in the Sacramento Valley by creating a food desert for tricolors. Even though former colony sites in tule marshes at National Wildlife Refuges were kept wet (for the endangered giant garter snake), tricolors failed to nest. Thus, rice fields seemed to have saved the day, and many rice growers made sure to report birds to the census teams.
The San Joaquin Valley colonies are mainly in grain fields near dairies and the fields are normally harvested a week or two before the tricolors finish nesting, which destroys the colonies. As in recent years, Audubon California and the federal Natural Resources Conservation Service worked with grain farmers to protect the birds, including paying them to delay or forego harvest. Federal funds for this run out next year, but there is an effort at Audubon to ask California government to make up the shortfall.
As always, the larger need is to establish more marsh nesting habitat away from dairies and other conflict zones, but the continuing severe drought has worked against this. One local bright spot is that the former nesting site in a thistle patch near North Regional Pond in Woodland could be rehabilitated if the site were irrigated this coming spring, and the City has offered to do so.
For more information about the lives and status of tricolored blackbirds, visit the web portal maintained by Bob Meese of UC Davis at tricolor.ice.ucdavis.edu or contact Xeronimo Castaneda of Audubon California at xeronimo.castaneda@audubon.org.
Michael Perrone, YAS Conservation Chair