Add another casualty to California’s prolonged and punishing drought: Wildlife officials warned this week that dry conditions in the state’s Central Valley could have a devastating effect on North American waterfowl.
The Central Valley is recognized as the most important resting and wintering ground on the Pacific Flyway, a global migratory path for millions of ducks, geese and other birds. About 5 million waterfowl spend the winter on state and federal wildlife refuge areas and flooded rice fields in the Central Valley each winter.
This year, the worst drought in a generation means those Central Valley habitats have been dramatically reduced in size. Wildlife refuges have had their state and federal water supplies cut by 25 percent. Rice acreage has been reduced by a similar amount as farmers also have endured water cutbacks.
As a result, millions of migrating birds will be crowded into less habitat, significantly increasing the odds of botulism outbreaks, which spread rapidly and can kill thousands of birds in a matter of days. The problem is not limited to rural areas but can affect waterfowl drawn to urban water bodies as well. Officials also are concerned the drought could cause food shortages.
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Already, at least 1,700 waterfowl have died at Tule Lake National Wildlife Refuge near the Oregon border. Between 10 and 20 ducks were found dead Tuesday in a canal that flows through Sacramento’s Pocket neighborhood, near Portuguese Community Park. A similar number of birds were found dead recently in a city pond in Hesperia in San Bernardino County. Avian botulism is suspected in each case, though laboratory verification is pending.
Adding to the threat this year is that breeding conditions for waterfowl in Canada have been very good. As a result, said Mark Biddlecomb, Western region director of Ducks Unlimited, a record number of birds will fly south this summer and fall in search of wintering habitat. Instead, they’ll find hundreds of thousands of acres of dried up rice fields and shrunken wetlands.
“We’ve got this perfect storm, if you will. And it’s not going to be pretty,” Biddlecomb said. “I think we’re looking at the probability of a food shortage in addition to a disease outbreak. If they don’t go back in excellent condition, they’re not going to be breeding like they would normally, and that will affect the entire flyway from the boreal forests of Canada all the way down to Mexico, frankly.”
On Tuesday, the California Department of Fish and Wildlife urged the public to help by watching for waterfowl that might be suffering from botulism. If outbreaks are caught quickly, the disease’s spread often can be halted and afflicted birds nursed back to health.
Symptoms of botulism include lethargy, paralysis, convulsions, and limp wings or neck. In addition, birds may attempt to propel themselves through water with their wings because their feet are paralyzed. Anyone who sees such symptoms, or dead waterfowl, is urged to report the details to the Department of Fish and Wildlife by calling (916) 358-2790 or online at: http://ht.ly/zLsnB.
Previous outbreaks in California have been responsible for as many as 46,000 waterfowl deaths in a single event. People, dogs and cats are generally thought to be resistant to the avian form of the disease.
“We haven’t seen this scenario in a long time,” said Dan Skalos, an environmental specialist at the Department of Fish and Wildlife. “I’ve been on some huge outbreaks before. It showed up one day, and within five days we had 5,000 dead ducks.”
The bacterium that causes avian botulism in waterfowl is common in wetlands throughout California. It is more likely to spread in warm water where rotting vegetation is found, which gives the bacteria something to feed on.
Krysta Rogers, also an environmental specialist at the Department of Fish and Wildlife, said people can exacerbate the situation by feeding waterfowl. People often feed bread to ducks and geese, which is not nutritious for them and causes them to produce large quantities of feces. This creates even more “substrate” for the botulism bacteria to spread, she said.
“At this time of year, particularly with these dry conditions, there’s just not as many natural places for the birds to go,” Rogers said. “So they tend to concentrate in places where they have this permanent water source, like city ponds or like the canals. When we have these warm conditions like this, it’s ideal conditions for the bacteria to grow.”
The waterfowl migration generally begins in mid-August, with the arrival of pintail ducks, and peaks in October. Some waterfowl already have begun to arrive in the area, including mallard ducks, and some are year-round residents.
Typically, they would find refuge in flooded rice fields this time of year. But the California Rice Commission estimates about 140,000 acres normally planted with rice, and kept in a flooded condition, have been left dry and unplanted this year because of the drought. That’s a 25 percent reduction.
In addition, state and federal wildlife refuges throughout the Central Valley have seen water supplies cut by 25 percent. This water, mostly provided by the U.S. Bureau of Reclamation, was reduced as part of a series of cutbacks to farms and cities. The cuts mean many refuges were unable to do early-season flooding that helps grow natural foods for waterfowl.
Lower Klamath National Wildlife Refuge along the Oregon border is almost completely dry already, said John Beckstrand, a wildlife biologist with the U.S. Fish and Wildlife Service. As a result, traveling waterfowl are congregating in greater concentrations in other areas, including nearby Tule Lake National Wildlife Refuge.
The Klamath refuge complex, which includes Tule Lake, experiences botulism outbreaks in two out of three years, Beckstrand said. But he expects conditions to be unusually bad this year. Within the last few weeks, volunteers have collected about 1,700 dead birds – mostly mallard ducks – at Tule Lake, which he said is an unusual number this early in the season. He estimates this is only about 40 percent of the actual deaths, because carcasses can be difficult to find.
The refuge operates a “duck hospital” to rehabilitate birds suffering from botulism. Simply keeping them cool and providing ample clean water allows the vast majority to recover in just a few days, Beckstrand said.
Dead birds are incinerated, and it’s important to collect them from the wild as soon as possible, he said. Otherwise they draw flies which produce maggots, which ducks love to eat. The maggots concentrate the botulism toxin, and it only takes one or two to kill a duck.
The problem may not go away even once winter arrives. That’s because rice farmers normally flood their fields in winter to decompose rice straw left behind after harvest. In an average year, this provides about 300,000 acres of winter waterfowl habitat in the Sacramento Valley. It also gives the birds easy access to remnant rice seed, a nutritious food source.
But few farmers have enough water this year to flood their fields after harvest. Paul Buttner, manager of environmental affairs at the California Rice Commission, estimates only 50,000 acres of rice fields will be flooded this winter. That’s more than an 80 percent reduction.
Instead of flooding, most farmers will plow their fields to bury the rice straw, which also buries much of the food left behind for waterfowl.
“There just isn’t going to be the water available around the Valley to be able to disperse the birds out to where they’ll be safe,” said Jeff Volberg, director of water law and policy at the California Waterfowl Association. “They’re going to have to crowd together on the refuges and wherever they can find suitable water bodies to feed on and spend the winter.”
The wildlife refuges may have problems of their own this winter. They’ve been ordered to stop diverting water entirely on Oct. 1 to preserve river flows for migrating endangered salmon. This means even the refuges will have a harder time maintaining habitat during the crucial winter period.
“It’s all going to depend, I think, on weather and luck,” said Skalos, of the Department of Fish and Wildlife.