Local bird advocates are up in arms about the deaths of what they say are dozens of songbirds that have gotten trapped in netting, recently installed by a Caltrans contractor under a Highway 101 bridge in Petaluma.

The birds are cliff swallows, small black and white songbirds with ruby throats that migrate to Sonoma County from South America in order to reproduce. They have traditionally nested under the bridges that cross over Lakeville Highway and Petaluma Boulevard South, according to Veronica Bowers, director of the Sebastopol bird rescue organization Native Songbird Care & Conservation.

Construction is taking place under the bridges in preparation for Highway 101 work.

The birds are apparently getting trapped in the netting under the Lakeville Highway span, which Bowers says is not properly installed, and dying when they can't get out.

Caltrans spokesman Bob Haus said that Caltrans put up the netting in February to comply with state and federal requirements for protecting migratory nesting birds. Those requirements state that such netting must be installed to keep birds away within 50 feet of a construction site.

He added that Caltrans has been aware of the problem since March 27, when it first found birds entrapped there, and immediately contacted the U.S. Fish and Wildlife Service, as well as the California Department of Fish and Wildlife. They've been working to correct the problem since then, sending the regulatory agencies 5-day reports to keep them up to date, Haus said. The agency hopes to have the problem fixed, meaning it will have closed any gaps between the netting and the structure of the bridge itself, by this Sunday.

The reason it's taken so long, Haus said, is the netting's location under the high spans.

"Access is difficult; lanes have to be closed at night," he said. "We're doing all we can, working night and day to correct the situation."

But Bowers and others questioned the time its taken to fix the problem and contended that the netting is doing more harm than good. "This is really shocking to me," Bowers said. "They're choosing to let these birds die a horrible death."

She says she first noticed the netting about a month ago, and recognizing that such a device can often cause problems for birds, called Caltrans. Two weeks later, she hadn't received a response, so she called again. Then, on Sunday, her suspicions were confirmed, Bowers said. She found about 17 dead swallows in the netting and two that were barely alive. The next day, she found 13, and on Wednesday 15.