Birds singing louder to battle plane noise

BIRDS sing louder to compete with being drowned out by aircraft noise, a nationwide study of nearly a million audio samples has found.

American researchers found human-generated noise has an impact on birds, even if there is no distinct or direct threat.

Surveying birds around national parks from across the US, birds increased their sounds by two per cent when aircraft sound was detected.

Scientists surveyed 894,060 clips, with data collected from 130 sites in 48 parks.

Doctor Kurt Fristrup, a National Park Service scientist, said birds were also likely to sing louder for hours after the aircraft has passed.

He said: “We might have predicted a decrease in our ability to detect the calls due to coincident noise.

“Still more unexpected, there is a statistically significant effect of the history of exposure. For aircraft sounds, the increased sound detection decays with time, but there is a measurable effect up to three hours.”

Dr Fristrup is still working on whether birds under common plane pathways sing naturally louder than those who are undisturbed.

He said: “Given the histories of noise exposure within our data, how much are bird sound detection rates increased above the natural, noisefree condition? We’re preparing a manuscript to provide more detailed documentation of these results.”

Dr Fristrup said, however, the presence of aircrafts will make this difficult. He said: “The extensive presence of aircraft noise exposure in time and space implies that birds are producing more sound in many locations.”