|Precociousness of function in the song of Grasshopper Sparrows|
|Bernard Lohr, Rebecca Hill, Samuel Hulse. University of Maryland, Baltimore County, Baltimore, Maryland, United States
Young songbirds go through a sensorimotor period in their first year in which song develops from subsong through plastic song into its final crystallized form. In Grasshopper Sparrows males sing two structurally distinct song types: the buzz song and the warble song. While buzz song is sung by all territorial males, only already paired males produce warble song. Interestingly, the timing of crystallization appears to differ for the two song types, with warble song crystallizing several weeks before buzz song. Clues to song function come from aberrant buzz song resembling some elements of plastic song that may be a product of atypical early crystallization. A male producing such song held a territory for four years at a field site in eastern Maryland, but was paired for only two breeding cycles in one year. To examine the intraspecific functions of this song we performed playback tests in which males were presented with normal adult song, aberrant song, and late plastic song. Territorial males responded at significantly greater levels to these songs than to controls, suggesting that while these songs are structurally distinct, they are functionally similar in this context.