Is Your Milk Killing This Endangered Bird?

The tricolored blackbird, which nests on dairy farms, just received emergency endangered species protection in California as its population plummets.

Robert Meese, a UC Davis researcher, with a tricolored blackbird. (Photo: Sylvia Wright/UC Davis)

Dec 10, 2014· 2 MIN READ
John R. Platt covers the environment, wildlife, and technology and for TakePart, Scientific American, Audubon, and other publications.

A century ago, millions of tricolored blackbirds covered California's wetlands and native grasslands. Those habitats are now almost gone, and the blackbirds aren't far behind. The species, which has been on the decline for decades, experienced its worst population loss over the past six years, when 64 percent of the birds disappeared. A survey released in July found that only 145,000 tricolored blackbirds remain.

To help stem the tide of this rapid population loss, the California Fish and Game Commission last week granted emergency endangered species status to tricolored blackbirds. The protections take effect immediately and will last for six months, after which they could be renewed or the birds could receive permanent protection.

The emergency designation provides the birds the same protections as any other wildlife listed under the California Endangered Species Act, which, like the federal Endangered Species Act, prohibits the killing, capturing, or hunting of listed species. A petition from the Center for Biological Diversity, an environmental group, requested that the state also require farmworkers to report nests, eliminate the legal hunting of look-alike red-winged blackbirds—which farmers are allowed to shoot as pests—and work with landowners in other regions to establish suitable nesting habitat. No specific decisions on those possible actions have been taken yet.

"The emergency listing is unfortunate but necessary," said Robert Meese, the staff researcher for the University of California, Davis, who coordinated the survey and has studied the birds for the past 10 years.

That research found that the birds have almost completely disappeared from four counties, including Colusa County, which only a few years ago had 80,000 breeding birds within the Delevan National Wildlife Refuge. "That may be the first time in the evolutionary history of the species that it did not breed in Colusa County," he said. "To have no evidence of breeding by tricolors in Colusa County in 2014 is a shock and unprecedented."

The decline of tricolored blackbirds appears to be linked to the shift in dairy production from Southern California to the San Joaquin Valley. The birds have found new homes on dairy farms, which devote large fields to growing a white-rye hybrid called triticale, which is harvested and stored in silos to feed their cows year-round.

"The birds found that the silage fields on dairy farms were a pretty good alternative to wetlands," said Michael Marsh, chief executive officer of Western United Dairymen, which represents about 800 dairies. "The silage fields actually provide pretty good protection for them to nest their young. It helps hide them from predators, whether they're hawks or coyotes."

But blackbird-breeding season also coincides with triticale harvesting season. In 2011, Meese found that harvesting the grain in certain fields resulted in the deaths of tens of thousands of birds at a time. One colony in Merced County had more than 33,000 nests, and Meese estimates that 60 percent of them were destroyed. "The owner had been contacted, and we thought that we'd reached an agreement with him not to harvest, but 60 percent of the field was cut anyway," he said.

Triticale has a very limited season. If it grows for too long, the cows have a harder time digesting it, meaning farmers need to buy additional grains to feed their livestock. This can increase their feed costs by 90 percent or more. To help encourage farmers to delay their harvest by about two weeks—enough time for young birds to leave the nest—the United States Department of Agriculture and other organizations established a program to compensate them for their losses. "We've been pretty good at convincing them to delay harvest of that silage in return for compensation," Marsh said.

Meese, however, pointed out that this voluntary approach still leads to large amounts of dead birds that have nested in silage fields. "I know of two silage colonies that were destroyed by harvest in Merced County this past April," he said.

Marsh said his association has not yet heard exactly how the emergency listing will affect farmers. "Instead of a voluntary collaboration, will USDA no longer fund the compensation so the birds can thrive?" he asked. "Does it mean the farmers will stop planning that silage crop? What restrictions will occur if birds turn up on your property?" He said the organization is not only researching those answers but looking for funding to see if biologists can encourage the birds to nest outside the triticale fields.

Meese said he hopes the emergency listing can help turn things around for tricolored blackbirds. "If the endangered species listing means that the silage colonies will be conserved, then whatever reproduction occurs there will be conserved and add to the number of young produced each year."

The birds need the boost. "The rate of decline since 2011 has been accelerating," he said, adding that even with this emergency listing, he fears that the worst is yet to come.