New research published in the journal Biological Conservation finds that for every decibel of added noise, the hunting ability of saw-whet owls declines dramatically.
Their odds of detecting prey fell 8 percent per decibel, while the odds of actually striking the prey they did detect fell 5 percent per decibel.
By the time noise reached 61 decibels—a little louder than a busy restaurant—the owls completely failed to even notice nearby prey.
Lead researcher Tate Mason, education coordinator for the Peregrine Fund’s World Center for Birds of Prey, says the research was inspired by early studies into bats, which found that the flying mammals had to increase their hunting search times when flying near noisy highways.
“We wondered if other acoustically specialized predators, in particular birds, could be facing the same scenarios.”
They set out to examine the problem.
Instead of highways, though, they designed their experiment to replicate the sounds produced by natural-gas compression stations.
“Compressor stations are relatively new in the landscape,” Mason says. “They are increasing, and they run 24 hours a day, year-round.”
That gives them more impact than highways or airports, which create a lot of noise during the day but can be much quieter at night when owls tend to hunt.
Although he suspected that the birds would have impaired hunting ability, the complete failure surprised him. “The impact was more profound than I thought it would be,” he says.
Bangor University lecturer Graeme Shannon led work on a paper that synthesized research into the effects of noise on all manner of wildlife.
“These are noise levels that can readily extend hundreds of meters from an active drill rig or a busy highway,” he says, “which in effect drastically reduces the suitable habitat for animals that need to hunt.”
Mason says that’s an important aspect of his research. “The quiet places on Earth are becoming few and far between.”
Protecting those naturally quiet spaces from intrusive noise, he says, will help acoustic specialists such as saw-whet, Great Gray, and Northern Spotted owls.
“We have the ability to know ahead of time that there’s a threat out there that could be compromising owl habitat:
If we deal with that before the population declines, we can do better at conserving our wild creatures.”