Traffic in large urban areas is causing songbird numbers to drop
A study carried out in Canada has concluded that the rising level of noise in urban areas could be preventing some species of songbirds from setting up a home in developed areas.
The researchers discovered that noisy surroundings masked the lower frequencies of bird songs which affected the way in which some species communicated.
Females who cannot hear all elements of a song could also perceive singing males as ill-suited mates, it was reported.
Darren Proppe, the co-author of the study told the BBC: "There has been a growing interest in preserving or increasing the biodiversity of songbirds in urban areas.
"At the same time we know that these areas have pretty high levels of anthropogenic noise.
Dr Proppe, now based at Calvin College, US, but carried out the study while based at the University of Alberta, added: "We sometimes find areas within cities that have what seems like suitable habitat, yet we get lower diversity (of songbirds).
"So we wanted to investigate the hypothesis that there was link between bird diversity and noise levels."
In order to do this, the team surveyed species at 113 sites in natural areas within the city of Edmonton.
"What we found was that the number of species we had at each location tended to be lower when noise levels were higher," Dr Proppe observed.
"The decrease in species richness was one of the study's major findings."
He also went on to mention that the study has also focused on seven species that inhabited the area to see if their numbers were affected by the increase in urban noise.
A number of criteria were set in order to select the species. These included the birds being relatively common across the study area; forest or forest-edge dwelling; some elements of the species' songs overlapped by the dominant frequencies of road noise.
Dr Proppe went on to explain that they discovered three of the species had ‘lower abundances’ in the locations that were noisier.
He also said that the team found that the presence of lower frequency elements in a song was predictive of whether a species’ numbers would be affected by noise.
He went on to say: "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.
"We certainly know that birdsong and the perception of songs by females for mate selection, so in the paper we did speculate that maybe this was a mechanism these observed declines were occurring."
He has also suggested that females may perceive a song to be abnormal if the lower frequencies are inaudible. And that this, over a period of time, could impact the abundance of the species as if adults were not pairing and mating.
Picture: Tony Alter