Cleared for Takeoff

Airport wetland restoration could reduce bird-plane collisions

When birds strike a plane, they can shatter the windshield, damage the engine, and force an emergency landing. So the Federal Aviation Administration (FAA) was understandably concerned when planners at a California airport proposed restoring wildlife-friendly tidal wetlands near runways. But a new study suggests the project could actually reduce the number of bird strikes, making the airport both greener and safer.

The Santa Barbara Airport encompasses about 174 hectares of Goleta Slough, a swath of wetlands housing coyotes, rabbits, birds, snails, and fish. The slough used to be a bay but accumulated sediment after years of cattle-grazing and drought followed by intense rains. As part of an airport expansion during World War II, the U.S. Army Corps of Engineers filled in much of the slough and built berms to keep out the tides.

The idea of restoring tidal flows to part of the slough was greeted with suspicion by FAA officials, who reasoned that “if it’s higher-quality habitat, it should attract more birds,” says Andrew Bermond, a planner at the airport. “And more birds equals more strikes.”

To find out whether these fears were justified, the airport commissioned a study to determine the effects of restoring a one-hectare patch. A team divided a basin into two parts, opening one part to tides and leaving the other closed. Biologists from URS Corporation observed birds in each basin over three years, as well as birds flying over the airfield.

By the third year, a reassuring pattern had emerged. Large birds such as geese and ducks, which are more likely to damage planes, were ten times more abundant in the nontidal basin. In contrast, the tidal basin attracted small birds such as common yellowthroats and Belding’s savannah sparrows. The team also found that dangerous bird flights over the airfield were less frequent to and from the tidal basin than to and from the nontidal basin.

While the findings may not apply to all airports on wetlands, the demonstration provides “a neat case study,” says Bermond. He expects airfield crossings to decline further as native plants in the tidal basin grow, discouraging crash-prone birds called killdeer from nesting.

—Roberta Kwok

Photo by Doug Sonerholm

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