Dead birds found below mud nests of cliff swallows beneath the Highway 108 overpass on Peaceful Oak Road have been reported to Tuolumne County environmental health staff and state health specialists, but as of Monday afternoon no one knows why the birds are dying.

Dead specimens inspected Friday and so far this week are not viable to test for West Nile virus, Rob Kostlivy, the county environmental health director, said Monday in a phone interview.

Cliff swallows are common, social song birds found across the North American west, according to bird scientists. They originally built their jug-shaped mud nests on the sides of cliffs, but bridge supports and the sides of barns are just as popular nest-building sites for swallows, according to the Audubon Society.

Beneath the Highway 108 overpass on Peaceful Oak, there are at least 80 swallow nests at the top of two concrete bridge supports and on the underside of the freeway deck. Around 12 p.m. Monday, remains of at least a dozen birds were on the ground. Bird droppings covered the bases of the bridge supports.

Forty to 50 feet above is where cliff swallows have built their nests. The birds vocalized to each other at times, several birds flitted in and out of nests, and other birds flew at high speeds away from and toward their nesting colony.

Phillip Weakley called The Union Democrat on Friday to report dead birds under the Peaceful Oak overpass. Weakley said he called state health West Nile and Zika specialists first.

“It could be the West Nile disease,” Weakley said Monday. “I know I’ve been bit by mosquitoes up here.”

Weakley said he lives on Peaceful Oak and he walks under the Highway 108 overpass every day when he walks to the Arco ampm store on Mono Way. He said he first noticed dead birds on Wednesday or Thursday last week. There were probably dozens of dead birds on the ground then, but some creature or creatures have been coming to eat the dead birds since then, Weakley said.

State health staff told Weakley to call his local health authority. So he called Tuolumne County, and county staff told him to go out and pick up some of the dead birds, to collect specimens, so they could come and collect the dead specimens from Weakley at Weakley’s place on Peaceful Oak.

Weakley said Monday he got pooped on while he collected dead bird specimens on Friday.

“If those birds died of West Nile,” Weakley said, “I want to know about it.”

Weakley said Monday county environmental health staff took the dead birds and told him they would call him back but they never did.

I knew a guy who caught West Nile down in Oakdale,” Weakley said. “Bit by a mosquito at Woodward Reservoir and he was in the hospital nine months. He went through hell.”

Kostlivy said he went out and collected four dead birds from a reportee on Friday but none of them were viable to test for West Nile virus, the disease that kills birds and can kill humans.

There are quite a few dead birds under the overpass but they’re too far gone,” Kostlivy said. “If the eyes are dry we can’t test them.”

Kostlivy said county environmental health staff returned to the location under Highway 108 at Peaceful Oak Road on Monday morning to look for fresh specimens. They have not found any so far.

Contact Guy McCarthy at or 588-4585. Follow him on Twitter at @GuyMcCarthy.