Are song sequencing rules learned by song sparrows?

Abstract

Although the effects of learning on song structure have been extensively studied in songbirds, little attention has been given to the learning of syntax at the level of song sequences. Here we investigate song syntax learning in two cohorts of hand-reared song sparrows, Melospiza melodia: an isolate group, consisting of four males raised with no exposure to external song models, and a trained group, consisting of 17 males exposed to recorded song sequences during the sensitive period for song learning. The isolate males followed three syntactical rules previously described for field-recorded song sparrows: (1) they produced their song type repertoires with eventual variety, repeating a song type multiple times before switching to another; (2) they cycled through their repertoires using close to the minimum number of bouts; and (3) they showed consistent preferences for singing certain of their song types more than others. The trained males were tutored with sequences with exaggerated eventual variety and cycling patterns and no usage preferences, but their syntax was little affected by any of these training features. One syntactical pattern that was affected by external experience was the rule that long bouts of a song type are followed by long recurrence intervals before that type is produced again. Isolate males showed no bout length/recurrence interval correlations while trained males showed reduced correlations relative to field-recorded males, implicating learning in the development of the normal pattern. Other songbird species have been found to preferentially use song type transitions as adults that they were tutored with as juveniles, but the trained song sparrows in this study showed no evidence of such effects.