While some songbirds are not put off by the constant loud noise of compressors on gas pipelines, their nesting success is diminished by the din.
According to Penn State research, eastern bluebirds and tree swallows were willing to establish their nests and lay their eggs near compressors. But their nesting efforts did not produce the same number of offspring as nests sheltered from the noise of the machinery.
“Birds did not prefer quiet boxes over noisy boxes, which suggests that they do not recognize the reduction in habitat quality resulting from noise,” said the co-author of the study Margaret Brittingham, professor of wildlife at the College of Agricultural Sciences.
“But bluebirds and tree swallows nesting in noisy nesting boxes spent less time hatching their eggs, hatched fewer eggs, and produced fewer young than their neighbors nesting in quiet nesting boxes.”
To reach this conclusion, the researchers conducted an innovative study that included continuous playback of recorded compressor noise, 80 never-before-used nesting boxes occupied by bluebirds and swallows, and behavioral observations with video cameras placed in boxes. .
Natural gas is one of the world’s fastest growing energy sources, with continued expansion expected in the development of shale gas in particular. Compressor stations pressurize the gas and push it through pipelines to consumers.
According to the Pennsylvania Department of Environmental Protection, approximately 555 gas pipeline compressors were in operation in Pennsylvania as of December 2019. They are often located inside remote forests.
“Loud, low-frequency noise emitted by natural gas compressor stations travels hundreds of meters in undisturbed areas,” said co-author Julian Avery, associate research professor of ecology and wildlife conservation. “Because shale gas development often occurs in relatively undisturbed natural areas that provide important habitat for nesting birds, it is imperative that we develop plans to manage and mitigate noise. “
The experiment, considered the first of its kind, was conducted at the Russell E. Larson Agricultural Research Center at Penn State in Rock Springs.
The researchers took many precautions to ensure that they only assessed the birds’ reaction to compressor noise and not other factors, controlling for the confounding effects of physical changes in the environment associated with compressor stations. as well as the strong tendency of birds to return. in specific places where they had reproduced before.
They established 40 pairs of nesting boxes to attract bluebirds and tree swallows to a site with no previous breeding population and immediately introduced the sound of the shale gas compressor to half of the nesting boxes before the birds returned to the area, while the 40 other nesting boxes served as witnesses.
“We took a risk in starting the study – we weren’t sure these birds would find and occupy our boxes,” Avery explained. “We were hoping that ‘if we build it, they will come.’ Bluebirds likely had other places nearby to nest, and tree swallows were just returning from Central America. There was no guarantee that they would meet our boxes.
Danielle Williams, a Masters student in Wildlife and Fisheries Science at Penn State and currently field coordinator for the Hardwood Ecosystem Experiment at Purdue University, led the work, monitoring video feeds from cameras placed in boxes for document changes in breeding behavior.
She noted that there was no difference in clutch size – the eggs laid – between noisy and silent boxes, and the feeding behavior of adults, known as provisioning, was also the same in both.
But she observed that both species exhibited reduced incubation time, hatching success, and flight success in noisy boxes compared to silent boxes.
The results, recently published in Ornithological Applications, demonstrate that compressor noise caused behavioral changes that resulted in reduced breeding success for Eastern Bluebirds and Tree Swallows.
Nest success – the probability of at least one fledgling – calculated from all nests that were initiated, was not affected by noise in any of the species studied, Brittingham pointed out.
“This suggests that noise did not increase depredation or dropout rates, but rather negatively impacted fitness by reducing hatching and flight success,” he said. she declared.
Contact Marcus Schneck at [email protected].