|
The tricolored blackbird forms the largest colonies of any North American land bird, often with breeding groups of tens of thousands of individuals. In the 19 th century, some colonies contained more than a million birds — enough to make one observer exclaim over flocks darkening the sky “for some distance by their masses.” But colonial nesting birds are actually more vulnerable to extinction than are other species: because a small number of colonies may contain most of the population, human impacts can have devastating results. Over the past 70 years, destruction of the tricolor’s marsh and grassland homes has reduced its populations to a small fraction of their former enormity.
ENDANGERED SPECIES ACT PROFILE
PROTECTION STATUS: Not listed
PETITIONED: 2004
RANGE: Primarily California’s Central Valley; also found in Riverside, Colusa, San Diego, Siskiyou, and Alameda counties; has been reported in Oregon and Baja California with rare sightings in Nevada and Washington
THREATS: Destruction of habitat due to agriculture, urban development, and wetland draining; predation; competition with other species; and possibly direct removal of birds from private property
POPULATION TREND: The population of tricolored blackbirds in the Central Valley declined by at least 50 percent between the 1930s and early 1970s, and an additional decline of about 56 percent of the remaining population was reported from 1994 to 2000. Population censuses indicate that the tricolor declined from an estimated 370,000 in 1994 to 240,000 in 1997 and 162,000 in 2000.
|
SAVING THE TRICOLORED BLACKBIRD
While the tricolored blackbird’s big breeding colonies make the species seem abundant to casual observers, its gregarious nesting behavior renders these colonies vulnerable to large-scale nesting failures. In agricultural habitat, tricolors experience huge losses of reproductive effort to crop-harvesting and other agricultural activity; every year, thousands of tricolors taking refuge in dairy silage fields — fields where grass is being fermented and preserved for fodder — lose nests to mowing during silage harvest. And the situation isn’t much better for birds in nature: in what little remains of California’s native emergent-marsh habitat, tricolors are vulnerable to high levels of predation. Overall, this species has been in decline ever since widespread land conversion began to take hold throughout California.
But while the threats to the tricolor continue, so does the U.S. Fish and Wildlife Service’s refusal to protect it. The Center submitted a petition to list the species under the Endangered Species Act in 2004, but it was ignored for more than two years, even after we sued the Service to remind it of its obligations. Finally, in late 2006, the agency completed its review of the listing petition — only to declare it inadequate in showing the bird’s need for federal protection. The tricolored blackbird was given no Endangered Species Act status at all, not even the weak position of a candidate species. So the Center must continue to advocate for the protection of both the tricolored blackbird and its habitat.
ACTION TIMELINE
+ CAMPAIGN LINKS
NATURAL HISTORY
+ MEDIA
Contact: Lisa Belenky
|
