Young sparrows learn to sing by listening to other birds' conversation, a study of their behaviour suggests.
University of Washington researchers say the sparrows tended to ignore solo bird song, choosing instead to eavesdrop on pairs.
The scientists broadcast different types of song via loudspeakers and found the young sparrows tended to fly towards adult male twitter.
The Proceedings of the Royal Society journal is publishing the findings.
The US research team used radio equipment to tag 11 male baby sparrows, which had not yet begun to sing, in Seattle.
The birds were exposed to five minutes of pre-recorded song, either from pairs of song sparrows, a sparrow and a tit or a pair of tits.
The research leader, Christopher Templeton, said he focused on male birds because female sparrows generally do not sing.
He said: "We measured how close the juveniles came to the speakers, how long it took for them to approach and their overall movements.
"They generally moved closer, faster and farther when they heard recordings of two adult male sparrows interacting than when they heard recordings of a solo sparrow singing," he explained.
Safety in numbers
He said: "They seem to be learning how to sing and interact by eavesdropping on interactions."
Dr Templeton said learning shared songs was important for young birds in the flock.
He said: "Having shared song is the basis of song sparrow communications. By listening to two birds, the juvenile can also learn how the songs are used, something he can't learn by listening to a single bird."
Dr Templeton said the reason for gravitating towards group song could be because there was safety in numbers.
He said: "The young bird could do this by directly interacting with a mature adult bird, but that is risky because he might be chased away or beaten up."