“Why does the marsh sound like it’s full of cats?” someone asked as I led a group to a stand of cattails.
I explained to them there were no cats—rather a colony of tricolored blackbirds (Agelaius tricolor), some of the most social and vocal birds in North America. The male’s distinctive, bizarre, and cat-like calls can distinguish them from their look-alike, the red-winged blackbird. Tricolors behave differently too: unlike their more territorial relative, tricolors live in groups year-round—breeding, foraging, bathing, and roosting together through the winter.
A century ago, tricolors were the most abundant bird in Southern California, and widespread elsewhere. Today, the species is listed as threatened under the California Endangered Species Act. Over 99 percent of the world’s tricolored blackbirds live in California, breeding in dense colonies scattered across the Central Valley, the Central Coast, and Southern California.
Decades of tricolored blackbird studies have focused on the birds during their spring to summer breeding season, but we still know next to nothing about what they’re doing during the winter.
So for 21 years, I have explored where they are, what they eat, where they’re roosting, and what they sound like as the days shorten. A retired avian ecologist from UC Davis, I’ve led the triennial statewide survey that monitors the tricolor population. I have trapped and banded over 107,000 tricolored blackbirds, from the Central Valley, the Coast Ranges, and Monterey County during the breeding season to Solano County in the winter, where, over a decade ago, I discovered at least 50,000 tricolors foraging on a sheep ranch. By banding birds across locations and seasons, I have begun to illuminate their wintertime lives.
I discovered tricolors often move over long distances from their breeding colonies to their wintering grounds. When breeding, birds often live near dairies in the Central Valley. Much is known about these breeding grounds. But over the winter, birds seem to seek out farms and ranches, especially in the Delta, where plows unearth a delicious insect and seed buffet. By banding and recapturing birds, I discovered that tricolors may fly several hundred miles—sometimes over a matter of days—between the Central Coast and the Central Valley, crossing large, tricolor-unfriendly expanses of California to search for those winter feasts. To protect tricolors, I realized, we cannot focus on only one portion of the species’ range or one part of the species’ life cycle; we must protect places hundreds of miles apart.
As they travel, groups of tricolors stick together—one could say that they have friends with whom they journey through life. From the hundreds of birds I banded in the winter on the ranch in Solano County, I recaptured four of the same birds at one place almost 100 miles away in Colusa County the next spring. Those birds had moved together from Solano County to breed together in Colusa County months later.
Sometimes, you can see these “friendships” at work. In winter, tricolors perform wild, dizzying flights at sunset as they return from their foraging grounds to their roost. Before descending for the night, they circle above the tule marsh in pulsing, whirling flocks. One evening, I watched the spectacular yet rarely observed display at a small marsh in Placer County, alongside a homeowner in Folsom, who was the first to ever report the location of a winter roost. As we observed the birds, we saw how smaller groups of birds would whirl around and around until other groups joined them. Only then did they all descend abruptly into the tules to spend the night. The homeowner concluded the tricolors were “waiting for their friends” to arrive before settling down to roost. Given what I have learned about the birds, she was almost certainly right.
Much remains to be discovered about the tricolor, California’s blackbird. You, too, may see or hear something that no one else knows about, and you may contribute to our knowledge of the species by reporting your observations of aggregations of birds to the Tricolored Blackbird Portal.
