Scientists are learning how noise affects Bay Area wildlife as they work to conserve wetland birds amid a roaring urban soundscape

Ornithologist Katie LaBarbera arrives at the Coyote Creek Field Station in Alviso about 45 minutes before sunrise — peak time for bird activity.

The early part of LaBarbera’s Sunday shift is peacefully spent capturing, banding and releasing birds in what they call a “little oasis of trees.” But around 9:00 am every week, their team of volunteers hears a cacophony of car horns from I-880, less than half a mile to the east.

“You become really aware of the noise when you get away from it for a little bit,” said LaBarbera, a science director at the San Francisco Bay Bird Observatory.

The Bay Area is a permanent or temporary home for 250 different species of resident and migratory birds. Noise can affect their stress response, interfere with their ability to listen for predators and prey, and alter their vocalizations. But for conservationists striving to preserve the region’s threatened bird populations, disturbance from traffic, airplane and other noise is an unavoidable backdrop—and one that, until recently, has been little studied.

Clinton Francis, a sensory ecologist and associate professor at the California Polytechnic State University in San Luis Obispo, started considering these impacts more than 20 years ago. He spent several seasons researching the response of nesting birds to noise from natural gas industry operations on Bureau of Land Management lands in San Juan County, New Mexico, and found that in survey sites where wells had compressors running, fewer species and individual birds were counted than when the compressor was switched off.

“I realized we knew hardly anything about how birds respond to noise pollution,” he says.

Scientists’ understanding of the impact of urban noise on birds advanced during the COVID-19 pandemic, however. When the Bay Area shut down in March 2020, researchers like Jennifer Phillips — then working with Francis through a National Science Foundation Fellowship — had been studying the songs of white-crowned sparrows in San Francisco and Richmond. They were able to record how the songs changed when the noise subsided. In a paper published in Science magazine, they reported that male sparrows sang more quietly and used lower frequencies when not having to compete with traffic noise.

But the pandemic’s muting of urban noise is long gone. And while the wetland birds of the South Bay don’t sing, they have to compete with urban sounds when they use vocalizations to communicate with each other and ward off predators.

The South Bay’s Salt Pond Restoration Project — the largest tidal restoration effort on the West Coast — provides habitat to the threatened Ridgway’s rail, an elusive species of bird that spends most of its time hiding in the tidal marsh where it nests. The project area also hosts about 10 percent of the population of endangered western snowy plovers. These tiny shorebirds now depend on the salt ponds and tidal flats — as well as on their normal habitat of sandy beaches — for nesting and foraging.

But the salt ponds are located directly under flight paths from Oakland Airport and Moffett Federal Airfield. Nearby highways and Union Pacific railroad tracks mean birds in the project area are constantly impacted by noise from planes, trains and automobiles.

Chronic noise “shrinks an animal’s perpetual word,” Francis said. When noise increases, the distance over which birds can hear sounds reduces.

While the effect of noise on rail species has not been studied directly, they vocalize at fairly low frequencies, which transportation noise tends to drown out.

Plovers, on the other hand, may be more sensitive to sudden noises. A large truck zooming by an otherwise quiet area, a barking dog or a cellphone ringing can create the illusion of a threat, causing birds to react.

“Episodic or intermittent noise is, I think, a bigger deal for wildlife than something steady or constant like highway noise or a data center or whatever else,” said Dave Halsing, project manager of the Salt Pond Restoration Project.

Francis recalls baby plovers on the Oceano Dunes near Pismo Beach on the Central Coast spending their nights darting away from their habitats, disturbed by off-road vehicles. The inexperienced chicks interpret the noise as an immediate threat and expend energy trying to evade it.

Still, Bay Area ornithologists and bird lovers are preoccupied with addressing more immediate threats of habitat destruction from further development, which means noise pollution is a lower priority.

“In conservation, we’re usually worried about the absolute emergency situation,” LaBarbera said.

Urban noise isn’t going away, but small changes can make a difference. Francis points to the growing number of cities enacting leaf blower regulations, which while they are often aimed at curbing emissions also help to reduce noise pollution. Switching to electric vehicles, choosing tire materials that generate less road noise, and adopting quieter jet engines can all help.

Managers of the Salt Pond Restoration Project are doing their part, taking steps to reduce noise in their own construction work when making trails or fortifying levees to reduce flood risk. They try to use less intrusive construction equipment, such as vibratory pile drivers. Halsing said the project is also required to implement buffer zones of several hundred feet between their construction work and certain species, including rails.

It’s a time-honored practice in conservation: Working for wildlife, while keeping one’s distance.