Where are the birds in Southern California ???? - AnandTech Forums

Virus Takes Steep Toll on BirdsAbout 50,000 have died of West Nile in the state, but biologists do not yet know the full effect the disease will have on the avian population

By Zeke Minaya, Times Staff Writer

While the West Nile virus has focused on the risk to humans, state officials and wildlife experts said the disease could eventually take its biggest toll on California's bird population, where estimates put the deaths at 50,000 and rising.

The West Nile moved into Southern California this summer, dead crows and other birds found lying in parks and backyards were among the first signs. Now the authorities are trying to develop an accurate tally of the losses while also making sure that endangered birds, including the California condor, are vaccinated against the virus.

"When the virus first hit, we would get reports from people who were literally seeing birds falling from the sky, dead, "said epidemiologist Brit Oiulfstad, who works with the Los Angeles County Department of Health. "Now the calls we get are from people asking, 'Where are all the birds?' "

The virus has been moving west across the United States since 1999, spread in part by migrating birds. Infected mosquitoes pass along the West Nile virus to both birds and humans. California's bird population is particularly vulnerable to the virus because it is a major migratory hub for millions.

"Waterfowl, songbirds, hawks, millions upon millions of birds fly through California," said Walter Boyce, a veterinarian and executive director of the Wildlife Health Center at UC Davis. "It's called the Pacific Flyway." It's one of the biggest concerns; the birds move through California, we're seeing West Nile spread with them. "

"That's the $ 64,000 question that everyone is asking and nobody answers," said Patricia Bright, an official with the American Bird Conservancy, based in Washington, D.C. "There is a potential for a big effect. We really do not know how many birds we've lost."

Birds belonging to the corvid family? which include crows, magpies and jays? seems especially susceptible to the disease, Boyce and others said. Officials have found fewer birds from other families that have been killed by West Nile, but are not sure why.

Scientists are puzzled, for example, about why pigeons? one of the most common birds in urban areas? do not appear to have died in larger numbers.

"But we do not really know about other species," Boyce said. "It could just be that corvids tend to live alongside humans and are easier to find and test."

Figuring out exactly how many birds have died has also proven difficult.

When birds die in the wild, 80% of carcasses are scavenged within 24 hours, said Bright. And sick birds would probably seek the safety of a secluded spot, making them even harder to find.

Until recently, health officials kept careful track of West Nile bird deaths as a way of helping the disease's spread spread around the state. But this summer, the West Nile began infecting humans, some agencies stopped collecting bird carcasses and testing them.

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Has the California Department of Health Services confirmed the deaths of 1,922 birds because of West Nile? mostly crows, jays and ravens in Los Angeles and San Bernardino counties.

The U.S. Centers for Disease Control and Prevention estimate that the current death toll of birds is often 10 to 100 times higher than the number of birds officials test.

Nationally, West Nile has been detected in 234 of the roughly 750 species of birds in North America, according to the CDC, including the bald eagle, the American robin, the Baltimore oriole, the great horned owl and the white-winged dove. Most birds that become infected with the virus die of encephalitis or meningitis.

Experts are especially concerned about species already near extinction. Species with large populations and robust reproduction rates, like the American crow and the finch house, can lose large numbers and still bounce back, experts said.

But for species such as the San Clemente loggerhead shrike, which is found only in California and has less than two dozen, or the California condor, of which only 234 survive, one outbreak of West Nile could

Michael Mace, curator of birds at the San Diego Zoo, said that every California condor has been inoculated with a vaccine originally developed by the CDC for horses. There is no vaccine specifically for birds, but the horse vaccine appears to work.

"If this vaccine is effective, how would it look? to the protection of other endangered species, "he said.

The same measure can not be taken for other birds, such as hawks and other raptors, that are far-ranging and hard to track.

"Every single condor is tracked, but for these other species it would just be impossible to locate them in the wild, vaccinate and then monitor," he said. infected 430 people and killed 11 in California, all of whom were either elderly or in poor health.

Experts say they will really know the long-term effects of West Nile only after the virus recedes, as expected by late October. And though some are worried about the fate of endangered species, most agree that California's ecosystem will emerge largely intact because most birds? like humans can adapt to West Nile.

"For an ecosystem to be healthy, it must be able to deal with stress," Boyce said. "West Nile is a new stress that has been placed into our ecosystem. It is not going to cause the ecosystem to collapse, but it is going to change it. We just do not know how."