Zebra finch youngsters learning to mimic adult songs lose ground but then recover whenever they sleep, according to an extensive study of recordings. After being awake several hours, the young males regain their mastery of the material and then improve on the previous day's accomplishments.
During their slow start each day, the birds' sounds vary a lot, according to Sébastien Derégnaucourt of the City University of New York. In the Feb. 17 Nature, he and his colleagues propose that during such a period of great variability, a learner reshapes his performance. Derégnaucourt compares the emerging song to modeling clay. "If it's really hard, you cannot change it easily," he says.