North Atwater L.A. River Bridge: Safe Enough for Birds?
At SWA Landscape's summer studio, a crowd of Los Angeles River advocates gathered to hear proposals of river interventions made by seven interns from around the country.
After Ohio State University student Ian Mackay explained his proposition, which included a rust-colored perforated bridge that would double as bird habitat, Travis Longcore, science director of The Urban Wildlands Group, lauded his proposal saying it would be better for birds than the "North Atwater bridge, which would probably kill birds with its series of wires."
Longcore's statement stunned the crowd and prompted a meeting with the Los Angeles River Revitalization Corporation (LARRC), who had a representative in attendance at the presentation.
According to Longcore, herons and egrets, which could normally be found in the area, aren't acrobatic birds. They wouldn't be able to quickly change course once they spot the series of wires distinctive to the design of the North Atwater bridge (officially known as La Kretz Crossing). "Once they're set their course, they're not used to looking for obstruction," said Longcore. Like large ships that take time to turn, so do large birds such as these.
"Herons also get a blind spot in front of their head when they fly," Longcore added. Birds in this family have a blind spot because of the position of their eyes and the tilt of their heads during flight. "They can look forward, but once they tilt their heads slightly to look down, they have blind spots in front of them."
During our conversation Longcore had admitted he had not seen the design until spring, long after public comment period had expired December 28. Once he had seen it, he shared the design with a few colleagues in California conversant with bird-friendly design, and posed the question: "Does this look like a bird collision risk to you?" Their reply, "You'd want to do something to make those wires more visible."
Though the bridge had a visible deck, its wires were narrow (between 1.75 to 2.5 inches, according to Longcore). "Birds going between habitats on the river would likely try to fly over the deck but may not notice the wires until it is too late."
To mitigate the possible danger of the bridge, Longcore had suggested adding bird flight diverters to the bridge's cables every 15 feet. It is a mitigation method used with the country's electric power lines. The reflective plastic plate, which hangs from a clamp and spins, would reduce bird collision by adding motion, reflectivity, and light emission to a structure designed to meld into the Los Angeles river landscape. (An example can be found here.)
His suggestion was taken into consideration, but ultimately set aside. "They have either decided that they don't mind that this project has bird issues, or they're too far down the process to change the design," said Longcore, "Basically, they said no."
LARRC isn't worried, citing the long CEQA process the project had gone through. "Based on a thorough review and public comment period, the California Environmental Quality Act (CEQA) process and subsequent document has determined that the bridge will pose no significant impacts on wildlife," wrote Jennifer Samson, LARRC project manager, in an email.
"Bridges like ours that use cables of a sufficient width and utilize lighting effectively facilitate the safe movement of avian species, which is important as we recognize the value of the river's riparian habitat to all kinds of birds," concurs Henry Ong of the city's Department of Public Works.
The agency, however, requested for examples of diverters that were used on other similar, cable-stayed bridges similar to the North Atwater bridge before they pursue the matter even more. It proved to be a difficult task, says Longcore, because the design for the bridge isn't so common. He has yet to find a cable-stayed bridge outfitted with diverters.
In North Atwater bridge's case, Longcore says there aren't any endangered species at risk, but he wonders, is it time for Los Angeles to work on its own set of wildlife-friendly design guidelines?
"This is an area where L.A. has exhibited no leadership, and we could," says Longcore. Already, bird-safe design guidelines are available in cities like San Francisco, Oakland, Portland, and in Minnesota.
As cities around the country grow, the more our infrastructure infringes on animal habitats; it shows just by looking at the local ecology. Analysis of the Audubon Society's annual Christmas birdcount showed that in the past 40 years, the average population of common birds has declined 68 percent. Nearly a third of bird species found in the United States have documented cases of collisions.
Manmade obstacles confound birds that understand the quirks of nature. Birds think they're flying into another green habitat, only to find themselves crashing into reflective glass. Artificial lights confuse night-migrating birds. Power lines become unexpected challenges.
"There's always a balance to be had between access to people, recreation, bike paths, and wildlife," says Longcore. Perhaps now, as projects are blossoming along the Los Angeles River, the city needs to figure out how to regain equilibrium between the manufactured and the wild.
Learn more about this issue by getting in touch with Travis Longcore at Longcore@urbanwildlands.org. Those concerned can request the U.S. Fish and Wildlife Service to look into the project, citing the U.S. Migratory Bird Treaty Act.
