A pair of Sedge Wrens recently bred in grassland just north of Philadelphia, the young leaving the nest September 9th or 10th. According to BNA young males begin to practice singing at about three weeks of age and sure enough I first heard subsong on October 6th. This recording is from October 14th, when the bird would have been 5 weeks out of the nest. The song is fairly unstructured but still bears a resemblance to the adult song. Sedge Wrens are unusual in that they do not learn their songs but improvise them (Kroodsma).