Urban noises have created such disturbance that songbirds have been forced to change the pitch and pace of their song, a study has found.
Melbourne University researchers found urban silvereyes are shifting their song to overcome city sounds of up to 80 decibels.
However, their country counterparts who deal with background noise between 35 and 40 decibels, haven't done any such thing.
"A whisper is about 30 decibels ... so 80 decibels is actually really loud," the Age quoted student and lead author Dominique Potvin, as saying.
Researchers heard the greatest change in the speed at which songbirds such as silvereyes vocalise each word.
"The city birds leave a gap in between each word and they sing a lot slower ... which is like us in a way because if you can't be understood, your speech does tend to slow down," she said.
But it's not just the song that has changed - the calls have too.
While songs serve to attract a mate or define territory, a bird's call warns of predators.
"This opens up the bigger question of whether the city birds are changing genetically, whether the city population and the rural population are actually splitting," Potvin said.
She said it was important for the conservation of birds in urban areas.
"They need a noise sanctuary, not just habitat in city areas."