The Madeleine Brand Show for November 23, 2011

Noise pollution is driving larger birds away, study says

A western scrub jay

By Minette Layne via Creative Commons

The western scrub jay is one of many types of larger birds being driven away by human noise pollution, according to a new study.

Thanksgiving is not a good time for turkeys. But a new study from the National Evolutionary Synthesis Center in North Carolina has bad news for other birds as well. The research found that many larger birds are being driven from their natural habitat by human noise pollution. Scientists worry this could have long term consequences for the environment around loud areas like cities and factories.

The researchers gathered data by studying a remote patch of land in northern New Mexico that was full of natural gas wells. Some of these well had pumps that were constantly making a low racket. Other areas had pumps that were turned off. This allowed the scientists to study bird populations at loud and silent locations that were otherwise the same.

Clint Francis headed the study and said that only certain types of birds were driven away by the pumps.

"What we ended up finding was that birds with the lowest voices or the lowest pitched songs and calls tended to avoid those noisy areas," Francis said. Birds with lower calls tend to be larger, like scrub jays and mourning doves.

"It might be that birds were avoiding these areas due to their inability to hear one another," says Francis.

Francis explains that birds with low pitched calls can’t be heard over human generated noise because such noise tends to be low frequency. It ends up masking the sounds of the bird calls.

And he points out, those calls are important for birds to communicate, protect their territory and find mates. When they can’t hear each other their social interaction suffers.

National Evolutionary Synthesis Center scientist Clint Francis says that when these larger birds leave an area they stop providing valuable services for the ecosystem. He points to the western scrub jay.

"One single western scrub jay will hide in scattered holes in the ground up to 6,000 seeds in one single season. They inevitably don’t find all of those seeds to eat later on. Many of those seeds end up germinating and becoming the next stand of trees."

Francis says these birds help cut insect populations as well.

Gail Patricelli studies bird behavior at UC Davis and said that not all noise pollution is equal. Her research found that traffic seems to have a bigger impact on birds than other types of clamor.

"So if road noise has a bigger impact," Patricelli explains, "then maybe it is also just disruption and startling and frightening the birds in some way." She thinks intermittent noise may be harder for birds to adapt too.

Some birds manage to buck this trend. Pigeons and crows are large and have low pitched calls, yet they do well in loud cities. Patricelli says what these birds lose in their ability to be heard over urban din, they make up for by being able to eat almost anything and nest almost anywhere. Unfortunately. Patricelli says, most birds are pickier about their homes and diets.


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