The Tricolored Blackbird is North America's most colonial nesting landbird. Found almost exclusively in California, a single breeding colony can teem with over 35,000 birds, sometimes all settled into a single field or small wetland to raise their young. While similar to the more widespread Red-winged Blackbird, the male Tricolored Blackbird is distinguished by its red shoulder patch with a bright white wing-bar.

In the 19th century, Tricolored Blackbird flocks were described as numerous and often consisted of hundreds of thousands of birds. Since then, the population has declined from several million to approximately 177,000 today. Over a 10-year period from 2007 to 2016, it is estimated the population declined by as much as 34%.

There are many reasons for this decline. But the loss of native wetland and nearby foraging habitats along the coast and in the Central Valley is the main issue. In more recent years, the species has become dependent on agricultural lands, with most of the largest colonies nesting in grain fields. A real dilemma develops as Tricolored Blackbird young typically have not yet left the nest before the time farmers need to harvest their crop, and harvesting destroys Tricolored Blackbird nests and young. In some cases, tens of thousands of nests have been lost in a single field.

Each year, these birds gather in highly social colonies to raise their young throughout the San Joaquin Valley, Sacramento Valley, Sierra Foothills, Central Coast, and Southern California. However, with the continuing loss of habitat and the places they need to survive are becoming scarcer. As a result of this continued habitat loss and drastic population decline, Tricolored Blackbirds were recently listed under California's Endangered Species Act thus highlighting the recovery of this species is more critical than ever.