Noise pollution is affecting birds' reproduction, stress levels and more. The good news is we can fix it.

(Press-News.org) New research led by the University of Michigan is painting a more comprehensive picture of how noise pollution is impacting birds around the world.

"The major takeaway from this study is that anthropogenic noise affects many aspects of bird behavior, with some responses more directly tied to fitness," said Natalie Madden, lead author of the new study. 

The research, published in the journal Proceedings of the Royal Society B, was supported by federal funding from the NASA Biodiversity and Ecological Conservation Program.

While earning her master's degree at the U-M School for Environment and Sustainability, or SEAS, Madden launched an extensive analysis encompassing data from more than 150 studies published since 1990. These studies covered six continents and 160 bird species.

"Several of the studies we pulled data from focus on a single species and a single noise source," said Madden, who is now a conservation science and policy analyst with Defenders of Wildlife. "Based on our assessment of this meta-analysis, we were able to generate a broader statement about trends we're seeing."

Generally speaking, the noises made by humans—coming from traffic, construction and other activities—are impacting birds' behavior, physiology and even their reproduction. 

Since 1970, bird populations have declined at a staggering rate, with 3 billion breeding adults across a range of species lost in North America alone. While human activities like land development and pesticide use have more obvious direct impacts on bird populations, the new study highlights that our noise pollution is also affecting how birds survive alongside us.

"Birds rely heavily on acoustic information. They use song to find mates, calls to warn of predators, and chicks make begging calls to let their parents know they're hungry," Madden said. "So if there's loud noise in the environment, can they still hear signals from their own species?"

In collecting the data, the team also dug into how shared traits across species mediated certain noise impacts. For instance, birds that live in cavity nests appear more likely to experience negative effects on their growth compared with birds that live in open nests. And birds living in urban areas tend to have higher levels of stress hormones than those living outside of cities.

Although noise is creating all sorts of negative consequences for birds, understanding this can be turned into a positive, said the study's senior author, Neil Carter, associate professor at SEAS.

"By synthesizing across these studies in a meta-analysis, we find that there are predictable effects," he said. "And if we can predict them, then we can mitigate them, we can reduce them, we can reverse them."

Furthermore, Carter said, there are already solutions at our fingertips. Just as buildings are integrating new materials and techniques to increase visibility and prevent birds from colliding with windows, there are ways we can adapt our built environments to stifle sound.

"Knowing all this, combined with the fact that it is technically possible to reduce and manage noise, this feels like it's relatively low-hanging fruit," Carter said. "So many of the things we're facing with biodiversity loss just feel inexorable and massive in scale, but we know how to use different materials and how to put things up in different ways to block sound. We know what to use and how to use it, we just have to get enough awareness and interest in doing it."

The study's U-M collaborators included Kirby Mills, postdoctoral research fellow at the Institute for Global Change Biology, and Karen Alofs, associate professor at SEAS. Clinton Francis, associate professor of biological sciences at California Polytechnic State University, was also a co-author.

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