The nylon netting draped over the Petaluma and Lakeville Overpass bridges along Highway 101 about 30 miles north of San Francisco was intended to deter cliff swallows from nesting under the concrete and steel structures.
Instead, it entangled, maimed and killed more than 100 cliff swallows, according to a lawsuit filed in U.S. District Court in San Francisco against Caltrans and the Federal Highway Administration.
The lawsuit accused the agencies of violating the National Environmental Policy Act and the Migratory Bird Treaty Act by injuring and killing cliff swallows without a permit from the Secretary of the Interior.
Each spring, cliff swallows migrate 6,000 miles from South America to nest in rocky cliffs, foothills and under bridges over and near the Petaluma River. The swallows typically build 500 nests under the Petaluma River and Lakeville Overpass bridges alone.
"Swallows will be returning to Petaluma in early March," said Veronica Bowers, director of the nonprofit group Native Songbird Care and Conservation and a plaintiff in the lawsuit. "And when they do, our vigilant monitors will be waiting for them at both bridge structures to make sure the transportation agencies do the right thing."
Under terms of the settlement announced this week, Caltrans also agreed to use hard surface exclusionary material such as plywood and vinyl to prevent swallows from nesting on areas of the bridges under construction during the 2014 nesting season. All other areas of these bridges will remain available for swallow nesting.
In addition, Caltrans will help pay for local community outreach and education programs about the nesting behavior of cliff swallows.
The federal highway agency is expected to sign the settlement within a few weeks.
The lawsuit was filed in May 2013 by Native Songbird Care, the Center for Biological Diversity, the Animal Legal Defense Fund, Golden Gate Audubon Society, Madrone Audubon Society and Marin Audubon Society.
"We expect this agreement will influence measures to protect migratory birds at other Caltrans construction projects," said Danny Lutz, an attorney with the Animal Legal Defense Fund. "The terms of this agreement will be enforceable by the federal court."