WatchList Species Account for Tricolored Blackbird (Agelaius tricolor)

Qualifies for the list as a Red List Species

Photo: USFWS

The range of the Tricolored Blackbird is the Central Valley of California and surrounding foothills, coastal and some inland colonies in southern California, and scattered sites in Oregon, western Nevada, central Washington (the first documented breeding was in 1998), and the western coast of Baja California. It withdraws from part of its range in the winter. More than 99% of the individuals are in California. Unlike the morphologically similar Red-winged Blackbird, the Tricolored nests colonially, forming the largest colonies of any North American passerine; one colony was estimated to include over 200,000 nests. Most of the large colonies are in the Central Valley. Needed for a colony are nearby water, foraging habitat of natural grassland, woodland, or agricultural cropland. The birds often change their colony locations from year to year. Populations have decreased dramatically, declining for example 37% from 1994 to 1997.

Once killed to control damage to rice and grain crops, it still undergoes large losses of reproductive effort from crop-harvesting activities, with colonies of up to 50,000 nests destroyed by harvesting and plowing of weedy fields. Land conversion of its favored habitat to agriculture and urban development also greatly affects the bird’s populations. Conservation measures include avoiding losses of colonies and their associated habitats and increasing breeding populations on public and private lands managed for the species.