Center for Biological Diversity

Protecting endangered species and wild places through
science, policy, education, and environmental law.




Contact: Monica Bond, biologist, (951) 961-7720 (cell)

SAN FRANCISCO, Calif. – The Center for Biological Diversity sued the U.S. Fish and Wildlife Service in federal court today for violating the Endangered Species Act by failing to act on a petition to list the tricolored blackbird (Agelaius tricolor) as an endangered species. Recent state and federally sponsored surveys documented that the population of tricolored blackbirds plummeted at an alarming rate during the past decade, indicating the species is in dire need of protection under the Act.

The highly social and gregarious tricolored blackbird forms the largest colonies of any North American landbird, with a single breeding colony often consisting of tens of thousands of birds. The species has been documented to nest in 46 counties in California, and small colonies also have been recorded in parts of Oregon, Washington, Nevada, and Baja California. But the heart of the tricolor’s historical breeding range – and home to the largest remaining colonies – is the Sacramento and San Joaquin Valleys and southwestern California. In the 1800’s, one observer described a wintering flock in Solano County as “numbering so many thousands as to darken the sky for some distance by their masses.” Another observer at the time noted that the tricolor was “the most abundant species near San Diego and Los Angeles…”

Some long-time residents of the Central Valley can still recall when the area once teemed with massive flocks of these birds. Now, however, tricolored blackbirds have grown increasingly rare as the extensive wetlands and native grasslands once used for nesting and feeding have been lost to urban and agricultural development.

Forced from their native habitats, many of the birds have adapted by nesting in agricultural crops, typically dairy silage fields. Unfortunately, this phenomenon has contributed to the species’ decline, as the harvesting of these crops often coincides with egg laying and hatching – with “disastrous results for the baby tricolored blackbirds, and the population as a whole,” said Monica Bond, Center biologist and primary author of the petition to list the species as endangered.

Much like the now-extinct passenger pigeon, the colonial nature of the tricolored blackbird makes it particularly vulnerable to extinction. Because the birds instinctively congregate into the largest breeding colonies possible as a defense again predation, a small number of individual colonies can contain a high proportion of the overall population. Thus, human impacts on these colonies can have devastating results. In fact, recent surveys documented about half the entire population nesting in just two colonies in the Central Valley – both in dairy silage fields – in which thousands of nests containing eggs and hatchlings were mowed down during harvest.

“This repeated loss of almost the total reproductive effort of the largest remaining tricolored blackbird colonies is pushing the species towards extinction,” stated Bond.

Published studies by the Center and others have reported that the Endangered Species Act has effectively prevented extinction for 99 percent of listed plants and animals. Species that were never listed and those whose listing was delayed were over 3,200 times more likely to become extinct than protected species.

“Without the protections of the Endangered Species Act, the tricolored blackbird will suffer the same fate as the once-abundant passenger pigeon – extinction,” noted Bond. “And future generations of Californians may lose one of our state’s most breathtaking natural wonders.”

Tricolored blackbird

The tricolored blackbird is a medium-sized bird (total length ranges from 12-24 centimeters) that breeds in dense colonies in California’s Central Valley, Coast Ranges, and southern California. Adult males are a glossy blue-black with striking red and white shoulder patches, while females are mostly black with grayish streaks, with a small but distinct reddish shoulder patch. Tricolored blackbirds typically eat insects but will also take grains, snails and small clams.

The tricolored blackbird once numbered in the millions; one biologist in the 1930’s reported 1,105,000 individuals in the Sacramento Valley alone. In the petition, the Center described five major studies that estimated the population size of tricolored blackbirds from the 1930’s to 2000. These studies – representing the best recent estimates of tricolored blackbird abundance – indicate that the global population had dropped to about 370,000 by 1994. Six years later the population had declined by another 50 percent to 162,000 individual birds. While the sheer size of some individual colonies can make the species appear abundant, the overall population clearly has declined dramatically over the past 70 years.

On April 8, 2004, the Center filed a petition to the U.S. Fish and Wildlife Service to list the tricolored blackbird as an endangered species under the Endangered Species Act. The Fish and Wildlife Service failed to conduct an initial scientific review of the petition with the 90-day period required by law; the agency is now 16 months late on conducting the initial petition review. The Center sent a 60-day notice of intent to sue the Service on July 12, 2005. Again, the Fish and Wildlife Service failed to respond. The Center filed the lawsuit today in federal district court in San Francisco.

View the petition here:

The Center for Biological Diversity is a non-profit, public interest environmental organization dedicated to the protection of endangered species and wild places through science, policy, education and environmental law. The Center has over 18,000 members throughout California and the United States.


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