Traffic noise is harmful to the city birds, say the scientists from the Vassar College in the US. In the environment, which is enormously polluted with the anthropogenic noise, the birds are leaving their ability to get the signal about the danger.
The American researchers tested how traffic noise affected the reactions of Black-capped Chickadees and Tufted Titmice to titmouse alarm calls, which warn birds that a predator is nearby.
For the experiment, the ornithologists were using the speakers set up near feeding platforms baited with bird seed. The devices recorded the birds’ responses to three different recordings – alarm calls alone, traffic noise alone and a combination of the two.
As a result, the traffic noise did not deter the birds from feeding. But the side effect of this was unexpected. The birds were leaving their ability to receive from other birds an important signal about the danger. but five times as many birds approached speakers when the researchers played alarm calls on their own compared with when traffic sounds were added.
“There has been lots of work on how anthropogenic noise affects vocal production, but much less on the response of animals to signals in the presence of noise. Additionally, a lot of this work focuses on song, but we were interested in how noise might affect responses to an anti-predator vocalization,”
said Megan Gall from Vassar College.
The scientists concluded that many vocalizations are evoked by the presence of a predator, and these signals are extremely important for the birds. The study suggests that traffic noise can reduce birds’ ability to hear an alarm call, potentially increasing their vulnerability to predators.