Central Valley Birds Suffered More Than 60 Percent Decline in Six Years
VAN NUYS, Calif.— The California Fish and Game Commission today enacted emergency protections for tricolored blackbirds in response to a petition filed by the Center for Biological Diversity in October. The commission has protected the tricolored blackbird under the California Endangered Species Act for 180 days. The Department of Fish and Wildlife will next evaluate the petition and recommend to the commission whether to protect tricolors on a permanent basis and impose limits on activities that kill or injure tricolored blackbirds.
“This species has been in a dangerous decline for years, so this is a very important step to protect tricolored blackbirds and their nesting colonies,” said the Center’s Jeff Miller. “Tricolors are particularly vulnerable to human impacts, because a small number of breeding colonies can contain most of the entire population. These new protections and limits on killing of tricolors are vital tools to try to help recover the population.”
Tricolored blackbirds once formed massive nesting colonies of millions of birds in California’s Central Valley but have declined dramatically due to destruction of wetlands and native grasslands, shooting, pesticide use, and mowing and harvest of crops used as nesting sites during nesting season. Comprehensive statewide surveys of the entire population of tricolored blackbirds found an initial count of 395,000 birds in 2008 followed by a decline to 259,000 in 2011 and only 145,000 in 2014 — the smallest population ever recorded.
Forced from their natural nesting sites by conversion of wetlands and native grasslands in the Central Valley to urban and agricultural development, many tricoloreds have adapted by nesting in agricultural crops — typically dairy silage fields. Crop harvesting often coincides with egg laying and hatching, and many eggs and nests are destroyed during harvests.
Recent surveys documented up to half the entire tricolored population nesting in just two colonies in the Central Valley in dairy silage fields where thousands of nests containing eggs and hatchlings were mowed down during the harvest — despite the fact that mowing of active tricolor nesting colonies is supposed to be prevented by California Fish and Game Code Section 3503, which protects all bird nests and eggs from destruction. An unknown number of adult tricoloreds are also killed each year by rice farmers, who are allowed to kill other blackbirds to protect their crops. Today’s emergency protection should prevent or significantly limit such activities during the upcoming spring nesting season for tricolored blackbirds.
“The commission has finally heard the warnings from biologists and conservationists about widespread losses of tricolored blackbirds and nesting colonies over the past two decades and taken action,” said Miller. “It’s crucial that harvesting and plowing activities on private lands used for tricolor breeding are prohibited or delayed during the upcoming 2015 nesting season — and that prohibitions on shooting are enforced.”
Over the past decade the California Department of Fish and Wildlife and other partners have initiated voluntary measures to save tricolor nests from destruction during crop harvest by making crop purchases or reimbursing farmers for delayed harvest on private agricultural lands where tricolors nest. Unfortunately these measures have not stopped the decline of the species or prevented destruction of tricolor nests on many dairy farms and other agricultural lands in the Central Valley. In 2011, for example, 56 percent of all tricolor nests in silage fields were destroyed despite efforts to contact farmers and coordinate buyouts of harvest delays.
The tricolored blackbird (Agelaius tricolor) is a medium-sized bird that breeds in dense colonies in California’s Central Valley, coast ranges and Southern California. The primary breeding range is the Sacramento and San Joaquin valleys. 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.
Tricoloreds form the largest breeding colonies of any North American land bird, with a single colony often consisting of tens of thousands of birds. These large breeding colonies are a defense again predation. In the 1800s one observer described a wintering tricolored flock in Solano County as “numbering so many thousands as to darken the sky for some distance by their masses,” and in the 1930s a biologist reported a flock of more than a million tricoloreds in the Sacramento Valley alone.
Tricolored numbers declined in the Central Valley at least 50 percent between the 1930s and early 1970s, and an additional decline of approximately 56 percent of the remaining population was reported from 1994 to 2000.