Alarming Swallow Die-off Sparks County Vet Investigation

by on May 30, 2008 · 0 comments

in Environment

Over 100 Local Deaths of Cliff Swallows At Otay Lakes Parallel 100 Deaths At Lake Arrowhead

By Mike Lee / Union-Tribune / May 30, 2008

The recent deaths of nearly 100 cliff swallows near the public dock at Lower Otay Lake – plus five deaths reported yesterday at El Capitan Reservoir – have created a stink and prompted an investigation by the county veterinarian. There’s no indication yet of a threat to human health, and an official determination isn’t likely until next week. Officials for the lakes, which are reservoirs for San Diego city, are monitoring the situation closely in case the cause is a toxin in the watersheds.

“I wouldn’t say this is normal to see a colony like that experience such a high number of losses. That is why we want to figure out what is going on,” said Nikos Gurfield, the county vet. His testing of the corpses isn’t easy. “The birds are small. They are often in poor condition.. . . By the time they get here they are a bit rotten, so I don’t want anybody to hold out for quick answer,” he said.

Gurfield is looking for west Nile virus and avian influenza, two diseases that have captured a lot of attention in recent years, as well as lesser-known possibilities. “My job is to consider everything,” he said. “I want to figure out if it’s a phenomenon that is restricted to the birds or if it implies some dangers to other animals or people.”

The problems appear to have started about a week ago, when the reek of decaying birds at the Lower Otay public dock caught the attention of the city’s lake manager. Swallow deaths have continued for several days, prompting reservoir employees to knock down nests that have dead swallows. “There are a few that are surviving, but most of the birds. . . and the babies are dying,” said Nelson Manville, supervisor of the the lakes program for San Diego. “They have had a horrendous smell.” Yesterday morning, he learned from employees at El Capitan Reservoir that they were seeing similar problems. El Capitan, the city’s largest reservoir, is about 30 miles northeast of downtown San Diego.

On Thursday, news reports circulated about the deaths of roughly 100 swallows at Rim of the World High School in Lake Arrowhead. San Bernardino County health officials said they suspected the birds were poisoned, but similarities between the Arrowhead and San Diego incidents are raising questions about whether there’s a broader factor at work. “Any time you have these large number of die-offs, it’s concerning,” said Jane Hendron, spokeswoman for the U.S. Fish and Wildlife Service in Carlsbad.

Swallows are common in most parts of California, and they often live near developed areas because they nest in rafters and other structures. They spend their winters in South America and are famous for their regular returns to San Juan Capistrano.

While some people consider the birds – and their droppings – to be a nuisance, they are protected by the Migratory Bird Treaty Act. Phil Unitt, a bird expert at the San Diego Natural History Museum, said he couldn’t recall a similar death spiral for a local population of the swallows.

But he has noticed a long-term reduction across the San Diego region. “The numbers of colonies of these birds have definitely dwindled over the past 20 to 30 years,” he said. “They used to be widespread around the city.” Unitt is puzzled by the Otay Lake deaths and hopes the situation will lead to a better understanding of population trends for the cliff swallow.

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