The researchers found that urban noise
severely cut down the range of calls - a
frog that could be detected 800 meters
away in the bush would only be heard 14
meters away in the city.
Image: iStockphoto
Birds and frogs are raising the volume of their calls to be heard above urban noise. Nerissa Hannink reports.
The noise of traffic, machinery and air conditioners may be driving birds with low-pitched songs away from cities while leading others to raise the pitch of their singing to be heard above the din.
Two studies from the University of Melbourne have revealed that urban noise is impacting on birds in Australia, Europe and North America.
Dr Kirsten Parris from the School of Botany and Ms Angela Schneider from the Department of Zoology found that some birds living on Mornington Peninsula roadsides are singing at a higher pitch in traffic noise.
“The grey shrike-thrush can live in narrow strips of woodland next to roads, and this species is changing its song in noisy locations,” says Dr Parris. “But once noise levels get very high, the chance of finding the birds is very small.”
Dr Parris says both cities and roadsides can provide important habitat for many species, if we work to reduce noise levels.
The study recommends the impact of traffic noise on animal communication be taken into consideration during planning. It also suggests reducing traffic noise by changing road surfaces, decreasing traffic speeds, or even re-routing roads during the breeding season when birds are most vulnerable to noise and passing vehicles.
In a second study, Mr Yang Hu and Dr Gonçalo Cardoso of the Department of Zoology studied more than 500 bird species across three continents, and found that those common in cities sang higher than related species that prefer the country life.
“Urban noise makes it hard for animals to hear each other’s calls and songs, and this is especially true for those who communicate using low-pitched sounds,” says Mr Hu.
“Birds that can’t be heard above the noise of the city may have trouble attracting a mate, maintaining a territory, raising their family, and warning other birds of danger from approaching predators,” he says.
Dr Parris and her colleagues recently found that city frogs are also calling at a higher pitch to make themselves heard in traffic noise.
Dr Parris has been researching nine frog species in public garden ponds.
She says that in areas where there is a lot of traffic, male frogs that could once be heard by females 800 metres away can now only be heard within 14 metres.
Being heard is important – female frogs are attracted to a chorus of males and move towards them, and then choose which male to mate with based on how he sounds.
The results of this research have been published in the international journals, Ecology and Society and Behavioral Ecology.
Editor's Note: Original news release can be found here.
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