Birds that are exposed to persistent noise from natural gas compressors and oil operations show physiological signs of chronic stress. As the new study states, the symptoms are very similar to those in humans suffering from post-traumatic stress disorder (PTSD).
The study was conducted by researchers from the University of Colorado Boulder and was published in the journal, Proceedings of the National Academy of Sciences (PNAS). According to the researchers, birds who gravitate towards noisier environments, such as western bluebirds, were reported to lay fewer eggs. The chicks that do hatch showed signs of stunted growth.
Lead author of the study, Nathan Kleist, claims that noisy environments impact both the birds’ stress hormones and their fitness.
“Surprisingly, we also found that the species we assumed to be the most tolerant to noise had the most negative effects.” States the scientist.
The authors believe this study sheds light on how man-made noise pollution affects wildlife. More so, they point out how stress from chronic noise exposure can harm humans as well.
In order to obtain the data, researchers monitored three species of cavity-nesting birds, including ash-throated flycatchers, and western and mountain bluebirds. These species were the most viable candidates considering they breed near oil and gas operations, in this case, located on Bureau of Land Management property in New Mexico. The researchers built 240 nest boxes on 12 pairs of sites.
Kleist and his team followed the birds for three breeding seasons, all the while taking blood samples from adult females and their chicks. Based on the blood samples, they evaluated hatching success, feather length, and nestling body size.
The study revealed that all species had lower levels of a stress hormone called corticosterone.
Co-author of the study, Christopher Lowry, says that low corticosterone levels are a common symptom for PTSD that can be found in both humans and rodents. He says that constant noise is able to keep the body’s flight or flight response activated to the point where humans and other species become sensitized. Researchers called this affliction “hypocorticism”, which was linked in the past with inflammation and reduced weight gain in rodents.
Kleist and his team found that noise pollution caused a hair-trigger response to the stress of being held for 10 minutes. They noticed that birds produced more stress hormones than those bred in quiet nests.
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