Urban birds have changed their pitch to combat city noise:
[Steve] Nowicki studies animal communication and says young songbirds learn from older ones, so after a while differences in style emerge. "We know that birds can be attentive to very subtle differences in their songs in the context of choosing whom to mate with," he says.
So if birds from the city can't flirt with birds from the country anymore, "those birds are actually going to be less likely to mate with each other," he says. "I mean, literally they're going to stop being able to speak the same language."
The Dish 