Song Sparrows (Melospiza melodia) are one of many bird species with complex songs and other vocalizations. Previous research shows that these sparrows learn most of their repertoire. While the ability to sing is innate, the precise songs are not. They learn most of this repertoire during their first year, between the time they leave the nest and the time they migrate. A new study adds some more detail to the picture: young sparrows learn by listening to vocal exchanges among their elders.
For the field study, the researchers radio tagged 11 male sparrows in Seattle's undeveloped Discovery Park. These birds were about two months old and had not yet begun to sing. The park has a year-round resident population of approximately l50 breeding pairs.The abstract for the study is here.
To test a young bird's reactions, it was first located by its radio signal and then the speakers were placed about 50 yards from the animal's location. Finally the bird was exposed to five minutes of pre-recorded song, either from pairs of song sparrows, a sparrow and a chickadee (effectively a solo sparrow) or a pair of chickadees (the control condition). All of the sparrow recordings were from birds that were no longer alive, so that the songs the young birds heard were not familiar. Chickadees commonly live in the same habitat as song sparrows, so sparrows are familiar with their songs.
That the juvenile birds approached the simulated interaction of two song sparrows but largely ignored the solo singing of a song sparrow lends support to the social eavesdropping hypothesis proposed by Beecher. This theory says young birds learn to sing by eavesdropping on singing between adult birds, rather than listening to a single bird or directly interacting with an adult.
As a side note, American birders will note that the BBC article on this Song Sparrow study contains an egregious taxonomy error.