'Traffic noise may make birds more vulnerable to predators'

Excess noise in the environment from sources such as traffic may make birds more vulnerable to predators by reducing their response to alarm calls, a new study has warned.
Researchers from Vassar College in the US 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.
Using speakers set up near feeding platforms baited with bird seed, they recorded the birds' responses to three different recordings - alarm calls alone, traffic noise alone and a combination of the two.
The traffic noise did not deter the birds from feeding, 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," said Megan Gall from Vassar College.
"Additionally, a lot of this work focuses on song, but we were interested in how noise might affect responses to an anti-predator vocalisation," said Gall.

"These vocalisations are evoked by the presence of a predator and so are closely linked in time with a particular stimulus," Gall added.
The study suggests that traffic noise can reduce birds' ability to hear an alarm call, potentially increasing their vulnerability to predators.

The study appears in the journal the Condor: Ornithological Applications.