The industrial noise from oil and gas operations is causing nearby birds to develop stress responses similar to people with post-traumatic stress disorder, according to a new University of Colorado study.

The study, published Monday in the Proceedings of the National Academy of Sciences, found some impacted birds have chicks whose growth is stunted and, in the case of western bluebirds, lay fewer eggs that hatch when nested near the chronic, human-caused noise researchers compared to the sounds of highway traffic.

“In what we consider to be the most integrated study of the effects of noise pollution on birds to date, we found that it can significantly impact both their stress hormones and their fitness,” said lead author Nathan Kleist, who conducted the field research from 2010 to 2014 and graduated with a Ph.D. in evolutionary biology in May. “Surprisingly, we also found that the species we assumed to be most tolerant to noise had the most negative effects.”

The research consisted of following western and mountain bluebirds and ash-throated flycatchers for three breeding seasons.

Kleist and his crew constructed 240 nest boxes on 12 pairs of sites for the cavity-nesting birds, which breed near oil and gas operations on Bureau of Land Management property in New Mexico.

The team took blood samples from adult females and their babies and analyzed the birds’ hatching success, nestling body size and feather length.

Universally, the birds nesting in spaces with increased noise had lower levels of a key stress hormone, corticosterone.

“You might assume this means they are not stressed,” said co-author Christopher Lowry, a stress physiologist in CU’s Department of Integrative Physiology. “But when organisms are under chronic stress that’s inescapable for long periods of time, the organisms adapt to dial down the stress response systems. You might think of this as making the best out of a bad situation, but there are negative outcomes associated with that.”

Similar responses in humans occurred from conditions such as PTSD, chronic fatigue syndrome, fibromyalgia and hypothyroidism.

Decreases in reproductive success turned out to be a consequence in this study, Lowry said.

Chicks in the most quiet areas of the oil and gas drilling sounds still had reduced feather growth and body size, along with those in the louder areas.

The loudest regions posed another problem: machinery noise overpowering bird calls signaling when predators were close, which stressed nesting moms and chicks.

“If you were trying to talk to your friends and your children and you were always at a loud party, you would get worn out,” Kleist said in a CU news release.

He stressed that noise pollution is not just a problem for oil and gas operations.

“To pick on oil and gas, exclusively, would be disingenuous,” Kleist said. “We’re all creating noise pollution, even when we just drive a car.”

Lowry described another concerning development called an “ecological trap,” in which birds choose to nest in noisier environments, unknowingly subjecting themselves to negative outcomes such as reproductive hindrances.

The birds might nest in loud areas because of competition from other birds or absence of predators.

“It may be analogous to people who choose to live under a flight path,” Lowry said. “They do it because it may be cheaper to live there, but then does that have negative outcomes for their health later on? Of course, the birds can’t make those kinds of calculations. They end up trapped there because they have to raise their offspring.”

He hopes this research starts a dialogue about the impacts of noise pollution on the environment.

“It’s easy to kind of accept human-made noise as just part of our modern environment, and that’s just the way it is,” Lowry said. “But is that desirable? This study would suggest it’s not.”

Elizabeth Hernandez: 303-473-1106, hernandeze@dailycamera.com