Human noise pollution impacts all North American breeding birds

North American birds face high levels of anthropogenic noise pollution, especially when they breed in human modified habitats.

Most research on noise pollution’s impact on birds in the past focused on specific areas, certain species, or specific noises like gas compressors, but researchers wanted to find out if human noise pollution impacted birds on a continental scale.

“We’re just making a lot of noise everywhere,” said Brian Klingbeil, a postdoctoral scientist at Auburn University’s School of Forestry and Wildlife Sciences.

Klingbeil led a study published in Global Ecology and Biogeography that tackled this question using a National Park Service database of sounds across North America, including human-caused noises. The database included about 1.5 million hours of recordings in almost 500 locations including national parks, forests, cities and other areas. Other research showed that anthropogenic noise interrupts nature sounds in national parks, but in this study, the team was in search of continental patterns.

They picked out the human noises from the database and overlapped that with data collected from eBird, a citizen science application that helps create a database of bird observations, from 2004 to 2011 on the numbers of birds breeding throughout the continent. Whittling down the eBird data was a challenge, but the team decided to use only full surveys of birds rather than individual sightings and ended up with 322 bird species. With models developed by co-authors from Cornell University they projected the probability of seeing certain birds across the country using factors like elevation, habitat, and time of year.

Klingbeil and his colleagues also incorporated vocal traits such as how long an average song is, how loud they are, pitch variation and other characteristics, in order to determine if complex songs were more sensitive to human-caused noise.

“The first thing that stood out was how ubiquitous noise pollution is across the country,” Klingbeil said. While species that breed in human modified habitats were associated with twice the level of human caused noise than those in forest habitats, even those in natural areas faced noise pollution. “Even birds associated with forest were still experiencing 2 to 3 decibels of noise pollution above natural levels,” he said.

The researchers also found no difference in migrant and resident species in response to human-caused noise. But when they looked at vocal traits to predict bird sensitivity to noise pollution, they found birds with more complex songs in areas with higher noise pollution.

Overall, Klingbeil and his colleagues determined that some effects of local anthropogenic noise pollution may not necessarily scale up on a continental scale yet. But managers should take into account factors like song complexity, and singing behavior when implementing conservation measures.

Human-caused noise can make it difficult for predatory birds such as owls to search out prey or make it difficult for birds to hear one another’s signals, which are important for mating and avoiding predators. Klingbeil said noise can also affect other animals like bats, amphibians and even endangered species like the Sonoran pronghorn, which avoids noisy areas.

“I think when it comes to restoration or looking for new places to protect, it’s going to be important for managers or decision-makers to take sound into account,” Klingbeil said. “If there’s more than one option, next to a highway is not as good as one that’s farther away.”