An Avian Cholera Outbreak at the Salton Sea Has Killed Thousands of Birds

The Salton Sea, a 35 mile-long saline lake that is also California’s largest inland body of water, is home to a wide array of wildlife and a vital stopover for migratory birds. But in the past few weeks, this oasis has been host to a gruesome scene: thousands of birds dying from an outbreak of avian cholera. The disease spreads quickly between individual birds, especially when they gather in flocks, and can cause lethargy, convulsions, and rapid death.

Among the victims are roughly 6,000 Ruddy Ducks, more than 100 Black-necked Stilts, and roughly 100 gulls that have fed on the carcasses of infected birds. American Wigeons, Northern Shovelers, and American Coots have also suffered losses, as well as other shorebirds, including Willets, American Avocets, Lesser Yellowlegs, and Marbled Godwits.

Tom Anderson, a biologist at the United States Fish and Wildlife Service, says the outbreak has been primarily concentrated in the southern part of the Sea and should be contained within the next week. The recent government shutdown delayed containment, he says, but now his team is using airboats to monitor the outbreak and clean up bird carcasses to prevent further diesase spread. The California Department of Fish and Wildlife is also assisting in this process, which includes using an incinerator at the Sonny Bono Salton Sea National Wildlife Refuge to destroy victims of the outbreak.

Avian cholera epidemics are not uncommon in the Salton Sea and other bodies of water in California, but Audubon California and the U.S. Fish and Wildlife Service say that the deteriorating conditions at the lake could increase the likelihood of such outbreaks. “As the sea becomes more salty, I expect the birds to concentrate more around the freshwater inflows, Anderson says. “And I would expect there to be a higher chance of disease outbreak.”

The sea has already lost fish species due to its increased salinity, and with it, the majority of its fish-eating population of American White Pelicans and Double-crested Cormorants. According to Audubon California, tilapia, an important food source for fish eating birds there, is currently disappearing because it's too salty for them to reproduce effectively.

The Salton Sea has been in need of serious conservation efforts for the past two decades, but making that a priority for the State of California has proven difficult, especially since the lake is considered by many to be a man-made mistake. Andrea Jones, director of bird conservation at Audubon California, is tired of hearing that argument.  “Yes, it was partly man-caused, but almost all the other wetlands in California are gone, so it’s a surrogate habitat and birds have come to rely on it, particularly shorebirds,” Jones says. “They don’t really have anywhere else to go because Tulare Lake, the Central Valley Wetlands—all these other places have dried up.”

Conservationists are worried that the Salton Sea will meet a similar fate. The Imperial Irrigation District, which supplies Southern California water by tapping the Colorado River, has historically provided the sea with fresh water. However, in 2003, responding to Department of the Interior cuts to water coming into the state, the irrigation district signed an agreement giving the State of California 15 years to come up with an alternate plan. By early 2018, not much had happened at the state level, and the sea was shrinking rapidly.

Last August, reversing decades of inertia, California passed a 10-year management plan that hopefully will finally resolve the deteriorating situation through nearly 30,000 acres of restoration projects. However, despite 280 million dollars already allocated for the work, no new habitat has been created yet. Arturo Delgado of the California Department of Fish and Wildlife says construction of the first major habitat project of about 3,800 acres will begin in 2020 and directly benefit numerous bird species of the sea, as well as inform future habitat construction.

While the management plan will mitigate the effects of a shrinking Salton Sea, it notably does not provide additional sources of fresh water, meaning that the Salton Sea will continue to shrink until it hits an equilibrium—one that is saltier and looks more like what one sees at Great Salt Lake. In a few decades, “the Salton Sea itself won’t look anything like what it is today,” Anderson says. But, he notes, as long as farming continues in the area, there will be a “tremendous” amount of water that will continue to flow into the basin. “The restoration effort is just trying to make the best use of that water,” Anderson says. “If they can make safe and productive habitat out of that water, the birds will benefit.”

In recent years, some groups have taken conservation efforts into their own hands. The Sonny Bono Salton Sea National Wildlife Refuge has nearly completed its own restoration project involving diking an old dry bay and providing the impoundment with a mixture of Salton Sea water and fresh water. The project will restore more than 500 acres for birds. The Torres-Martinez tribe, situated on the northern side of the sea, is also on the verge of completing a habitat restoration project ahead of the California government.

As the state carries out its management plan, it will need to consider outbreaks like the ongoing avian cholera epidemic. The plan has a lot of potential, Anderson says, but scale is important for reducing the chances of another outbreak due to crowding. “If they only build a few portions of it, those areas might have a similar effect in concentrating birds,” and could increase the casualties, he says.  

Still, all parties remain largely optimistic about the state's plan. Ryan Llamas, Audubon California's Salton Sea program associate, says he is hopeful that the restoration projects will start to improve conditions at the Salton Sea. “It will be a good opportunity to see how humans can have a positive effect on their environment," he says.