A recent study has found that birds exposed to constant noise from oil and gas operations show physiological signs of chronic stress and -- in some cases -- have chicks whose growth is stunted. For the study, the researchers followed three species of cavity nesting birds, including western and mountain bluebirds and ash-throated flycatchers, which breed near oil and gas operations on Bureau of Land Management property in New Mexico. For three breeding seasons, the team took blood samples from adult females and their offspring and assessed hatching success, nestling body size and feather length. Across all species and life stages, the birds nesting in areas with more noise had lower baseline levels of a key stress hormone called corticosterone. When the fight-or-flight response is constantly revved, the body sometimes adapts to save energy and can become sensitized. Such "hypocorticism" has been linked to inflammation and reduced weight gain in rodents. Previous research has shown that some bird species opt to leave noisy areas. But the new study shows what happens to those which remain.
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