Pollution ruffling birdlife’s feathers

Acoustic degradation is even not for the birds, study shows

THE WESTERN bluebird didn’t realise what she was getting herself into when she chose her new home, about 68 metres from a natural gas compressor. It was only as the days and weeks wore on that the low whine of machinery started to take a toll. It was harder to hear the sounds of approaching predators, or the normal noises of the surrounding world, so she had to maintain constant vigilance. Her stress hormone levels became so skewed that her health deteriorated.

She couldn’t resettle elsewhere because she had hatchlings. Her chicks suffered too, growing up small and scantily feathered – if they survived at all.

Scientists sampled her blood, as part of a study of 240 nesting sites surrounding natural gas treatment facilities in northern New Mexico. They found she showed the same physiological symptoms as a human suffering from post-traumatic stress disorder (PTSD).

“Noise is causing birds to be in a situation where they’re chronically stressed… and that has really huge health consequences for birds and their offspring,” said Rob Guralnick, associate curator of biodiversity informatics at the Florida Museum of Natural History.

It would be a stretch to say noise hurts birds’ mental health – the animals have not been evaluated by an avian psychologist. But in a paper published on Monday in the Proceedings of the National Academy of Sciences, Guralnick and his colleagues say there is a clear connection between noise pollution, abnormal levels of stress hormones, and lower survival rates. This is the first time that link has been established in a population of wild animals, they argue, and it should make us all think hard about what our ruckus is doing to the Earth.

The research was conducted at the Bureau of Land Management’s Rattlesnake Canyon Habitat Management Area, a sun-drenched expanse of sage-brush-covered mesas and steep canyons forested with juniper and pinyon pine. The site is uninhabited, but it’s dotted with natural gas wells and compression stations that emit a constant, low-frequency hum.

Clint Francis, an ecologist at California Polytechnic State University, has been studying this ecosystem for more than a decade. In previous reports, he has stated that noise can restructure entire communities – prompting birds to alter the pitch of their songs. He found some species fared better when they nested near noise sources because the clamour drove away predators.

“But we were still concerned there might be hidden costs. That’s why we wanted to look at stress hormones,” Francis said.

Blood tests revealed levels of corticosterone in birds closest to the gas compressors were lower than normal. This initially came as a surprise. They took their results to Christopher Lowry, a stress physiologist at the University of Colorado at Boulder. To him, the results weren’t surprising – it’s what you would expect in a creature exposed to prolonged, persistent strain.

It will be hard to figure out exactly what’s happening, Francis said, because there are so many interconnected factors. For one, the birds might be stressed by noise but so are the animals that eat them. – Washington Post