EDMONTON, Alberta, March 11 (UPI) -- The noise of human activities may be driving songbirds out of urban habitats by drowning out their songs, Canadian researchers say.
Scientists from the University of Alberta said they have been trying to discover why some apparently suitable habitat in cities is relatively bird-free in the breeding season,
"We sometimes find areas within cities that have what seems like suitable habitat, yet we get lower [songbird] diversity, so we wanted to investigate the hypothesis that there was link between this and noise levels," lead study author Darren Proppe said.
A survey of bird numbers at more than a hundred sites in Edmonton, Alberta, suggested the higher the noise levels the lower the bird diversity, the researchers said.
The absence of a species at a particular site was also more likely if that species' songs relied on lower frequencies, they said.
"This potentially could be down to the fact that those lower frequencies could be overlapped by the dominant frequencies of road noise, which also tend to be fairly low, resulting in a masking of communication between birds," Proppe told BBC News.
In addition to making communication between birds difficult, Proppe said, some female birds might perceive males as unfit for breeding if they could not hear the full range of their songs.
If the birds were not mating as a result of this the population of each species would naturally decline, he said.
