Toronto: Birds flee from the path of an incoming car on the basis of the posted speed limit, rather than the actual speed of the vehicle, a new study has found.
Unlike their rural cousins, urban birds adjust their song frequencies to account for noise pollution, and they tolerate closer contact with humans, researchers said.
Pierre Legagneux, a behavioural ecologist at the University of Quebec and colleague Simon Ducatez, from McGill University, calculated the distance at birds would take off with a vehicle bearing down, `Vancouver Sun` reported.
Legagneux said the discovery could help conservation efforts.
"I expected to find that birds of course would react to my own vehicle ... But I found it was not the case at all. We found that birds were reacting to the average speed of the road," he said.
Researchers captured 25 species in flight, looking at reaction distances for all species, and for the three most prevalent the results were similar.
The birds appeared to have habituated to the local speed limit as one of the features of the landscape, researchers said.
They believe birds are also responding to "artificial selection," after less cautious birds were eliminated.
"Perhaps risk-prone individuals may have been killed, and only the shy individuals (survived)," Legagneux said.
Scientists found that the average distance birds allowed between themselves and the approaching vehicle before initiating flight was shorter in spring and summer than in fall and winter, the report said.
The believe this could be because naive, juvenile birds present in those early seasons were no longer around during the autumn.
The study was published in the journal Biology Letters.