Environment
Nate Schweber
TULE LAKE NATIONAL WILDLIFE REFUGE, Calif. — The corpses of ducks float like rags among the tall, green bunches of tule grass that partition the broad, flat water in this Northeastern California wetland.
United States Fish and Wildlife Service biologist John Beckstrand powers through here daily in an airboat with Steve Albers, an intern, at the bow. Albers grabs at dead birds with long-handled pincers, the type used to pick up trash from the ground, and slaps the sodden bundles into heavy-duty black garbage bags.
“I’m glad we got that one. Look at all those maggots,” Beckstrand says as Albers plucks from the water something that once looked like a mallard duck but now resembles an old mop used to wipe up spilled rice.
An estimated 10,000 ducks and geese here, plus many others around the state, have been killed this year by outbreaks of avian botulism, a bacterial disease related to the deadly botulism that humans fear from improperly canned food. A third year of drought in California, this one the most extreme, has created what Beckstrand calls a perfect storm of an environment for botulism bacteria to explode. Worse, by shrinking reservoirs, ponds and wetlands, the drought has decreased the amount of surface water where waterfowl can spread out, thereby concentrating them in sloughs where this contagious disease is most severe.
“And the problem is, we don’t know how wide it’s going to spread or when it’s going to end,” he adds.
The colossal Central Valley of California is part of a vital bird migration route known as the Pacific Flyway. Before European settlement, the Central Valley gave wintering grounds for some 40 million waterfowl. In modern times, 95 percent of the wetlands were dried for agriculture, and now the valley grows about a quarter of all the food eaten in the United States. But the land still supports an estimated one-fourth of all the migratory birds in North America, biologists say. Starting in late summer and building to a crescendo by late fall, some 4 million to 7 million waterfowl course south down the Pacific Flyway, particularly ducks, geese and swans that summer in Alaska and on the prairies of Canada. These birds take rest breaks in all the waterways along their migration route.
While it’s a neurotoxin, avian botulism exists naturally, in nonlethal quantities, in the soil of waterways and wetlands, scientists say. It is not a threat to humans. The problem is that the bacteria turns virulent in water that is low, warm and sapped of dissolved oxygen — precisely the conditions created by drought.
“It creates this continuous cycle,” says Krysta Rogers, environmental scientist for the California Department of Fish and Wildlife.
In late July, Rogers’ department sent out warnings across the state asking people to be on the lookout for bird corpses or struggling waterfowl that appear to be sick. In addition to the Tule Lake National Wildlife Refuge, birds with botulism have appeared in Sacramento, its suburbs, the surrounding valley and San Bernardino County.
In nondrought years, botulism outbreaks taper off in autumn, when temperatures fall and seasonal rains bring washes of clean, fresh water. But again, signs for this year are ominous, biologists say.
Chief among them is a change in agriculture practice by growers of rice, one of the most prominent of the 230 different crops grown in the Central Valley. Since the 1990s, rice farmers have flooded their fields after their harvest in order to break down the spent rice stalks and return their nutrients to the soil.
The flooded fields then provide food in the form of waste rice grain, decomposing vegetation and insects for an estimated 50 percent of all California ducks, geese and swans, biologists say. These fields also serve as wetlands that give waterfowl more places to spread out should there be a flare-up of any avian disease.
This fall, with so little water, California rice farmers are expected to flood perhaps one-sixth the number of acres they would in a nondrought year, according to the California Rice Commission.
“We typically have 300,000 acres of rice fields flooded in the winter. It may be only 50,000 acres or less this year,” says Mark Biddlecomb, of the sportsman’s conservation group Ducks Unlimited. “Given the conditions of the wetlands, and the lack of winter-flooded rice, we estimate that food resources will be exhausted by mid-December, just when duck numbers are peaking here.”
Through the state’s massive public works infrastructure, most of the water that flows naturally in California is siphoned to agriculture fields and city taps, and some of what is left is allocated for salmon rivers and waterfowl marshes. Because of the drought, the U.S. Bureau of Reclamation has cut the water allocation to some wildlife refuges in the Central Valley by 25 percent.
The effects of the drought are most pronounced in the Klamath Basin National Wildlife Refuge Complex, a crucial 192,000-acre part of the Pacific Flyway that spans the border with Oregon and includes Tule Lake. For the second year in a row, the wetlands at the neighboring Lower Klamath National Wildlife Refuge dried completely (a bill introduced by Democratic Senator Ron Wyden of Oregon that would allocate more water to the refuge from the reservoir at Klamath Lake was stalled in committee by Republicans in the House of Representatives). This has forced tens of thousands of migrating waterfowl onto Tule Lake, site of the state’s worst outbreak of avian botulism.
“All the birds are focused on this one refuge, and by concentrating them in a smaller area, that increases the likelihood that they will get botulism,” says Greg Austin a deputy refuge manager at Tule Lake. “If we were able to spread the birds out, we’d be better able to manage it, and lessen the impacts.”
To fight botulism, biologists take boats out onto Tule Lake to remove the dead birds, because they are incubators for disease. As maggots eat at the corpses, the bacterium concentrates inside their bodies. When other ducks eat those maggots, they too get infected, thus exacerbating the cycle.
“At best we kind of just scratch the surface,” biologist Beckstrand says as he scouts Tule Lake for dead ducks. “I think we underestimate what our total losses are.”
A few times per trip, the biologists catch struggling live ducks, weakened by botulism. Immediately after capture, a rubber tube is run down their throats, and into their stomachs is pumped a fat syringe full of fresh water, to counteract their dehydration. They are whisked to a fenced-off area in the refuge that biologists call the duck hospital. There they are given more fresh water and places to rest in the shade. Around two-thirds of these birds recover, biologists say.
Meanwhile, the more than 100 corpses of birds collected each trip are incinerated, to prevent further transmission of disease.
Many waterfowl species don’t migrate into California until well into fall, after botulism outbreaks usually die down. But scientists warn that if this drought stretches into the winter, this year could be different. Already the disease is taking a heavy toll on waterfowl that begin their migrations in the late summer, like Northern pintail ducks.
The botulism is also having a disproportionate affect on colorful and popular mallard ducks, biologists say. Mallards in California shed their worn-out feathers in the summertime and then grow new ones in a process known as molting. Male mallards, called drakes, molt first, then females, called hens. During the molt, these mallards are rendered flightless, making them susceptible to disease. Because the hens molt second, during the warmest months of the year, when botulism outbreaks are at their worst, they are hit hardest. This can hurt the overall population because fewer hens means fewer eggs.
“In many cases, birds that are being lost are the cream of the crop, those adult, female mallards during their flightless period,” says Mike Wolder, a supervisory wildlife biologist at the Sacramento National Wildlife Refuge Complex. “When they drop their feathers, they’re there for pretty much a month, so if there’s an outbreak, they can’t get away.”
Such waterfowl die-offs directly affect an estimated 80,000 waterfowl hunters, who spend millions annually, in the state of California. Around 65 percent of seasonal wetlands in central California, supporting more than 200 species of birds, are owned by and managed with funds from private duck hunting clubs, says Fritz Reid, a director of conservation programs for Ducks Unlimited.
“The drought will make many of these private wetlands remain dry until winter rains occur. Less monies will be spent in local communities for gas, food, et cetera,” Reid says. “A continued drought this winter would be catastrophic.”
This year’s twin punches of drought and botulism now have wildlife biologists bracing for what could be a third blow: avian cholera. That disease, transmissible from bird to bird, breaks out in wintertime, when food is most scarce, and when waterfowl burn the most calories to keep warm. Environmental stress, like drought, might add to the severity of an avian cholera outbreak, biologists say. This disease can quickly rip through flocks of Ross’s geese and snow geese, ruddy ducks, American coots and tundra swans.
“If this drought ends up being a sustained thing, we’ve got a problem — last year was bad enough, and the year before was not too good either,” says Dan Skalos, an environmental scientist for the state Waterfowl Program. “You compound these things a third year in a row, you kind of have to start to wonder if this is a sign of things to come.”
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