NORTH SHORE -- Another duck die-off hit the waters of Clear Lake this weekend, claiming 1,145 waterfowl as of 4 p.m. Experts are tentatively saying avian cholera is the culprit this time, pending lab confirmation.

Avian cholera affects birds so quickly that they have been known to sometimes literally drop out of the sky or die while swimming, according to the National Wildlife Health Center. Approximately 40 percent of the affected birds die; those who don't become carriers.

According to Record-Bee outdoor columnist Terry Knight, although all waterfowl are susceptible, the ruddy duck is Clear Lake's most common carrier. Approximately 3,000 ruddy ducks winter on Clear Lake, he added, which can easily turn into more than 10,000 in a matter of days.

Almost 230 dead ducks were picked up this weekend by the Department of Fish & Game, with some help from local residents. The birds, all ruddy ducks, washed up on the shoreline stretching along Highway 20 between Nice and Lucerne.

Crews on two air boats and a lead biologist from the North Central Region of the Department of Fish & Game arrived Monday afternoon to find about 350 more between Nice and Lucerne and 600 in Paradise Cove. Officials said most of them were ruddy ducks; a few mallards and gulls were also found dead.

Lake County Fish & Game Warden Lynette Shimek said she and the crews expect to work "however long it takes to get the birds cleaned up," possibly stretching into days.

Shimek added Monday night that anyone who finds dead waterfowl along the shoreline should not touch them or attempt to pick them up, but call DFG. Shimek can be reached at 275-8862.

"The birds have not been tested yet," said Shimek Monday morning. "So although this looks like cholera, we can't be guaranteed that that's what it is until they are tested."

So far five samples are ready to go to DFG's Wildlife Investigations Lab in Rancho Cordova, according to Associate Wildlife Biologist Paul Hofmann of the North Central Region of the Department of Fish & Game. There, they will undergo necropsy (the equivalent of a human autopsy for animals) and tested for a variety of diseases.

According to a Jan. 11 DFG press release about an avian cholera outbreak in Butte Sink less than 100 miles east of Lake County avian cholera die-offs usually happen during the winter months in California, especially during cold spells and fog.

Hofmann said outbreaks are usually ending about this time of year, and termed this outbreak "unusual." If avian cholera is to blame for the die-off, he said, it may have been aggravated by the recent cold snap.

"Stress and crowding is bad for people and birds," said Hofmann. "It's the same as with humans ... your resistance is low under stress."

As with any bird disease, said Hofmann, avian cholera is spread when birds concentrate in one area. He added that they tend to fly less and congregate more under stressful conditions.

The virus spreads through mucus when the birds are in close proximity to each other by sneezing, shaking their heads, grooming and pecking each other, and even through a spray emitted through their nostrils when they take off for flight, said Knight.

"You don't stop this," said Knight. "It runs its course, and then the birds leave," he said.

Hofmann noted that recent sunny skies and wavy conditions on the lake from high winds tend to break up mucus on the water surface, making for bad conditions for the spread of avian cholera. He further noted that the ruddy ducks will be heading north again in a couple of weeks.

Lake County saw close to 8,000 waterfowl die during an outbreak of avian cholera in January of 2004.