STRUCTURE OF LARK SPARROW SONG IN CALIFORNIA.

We studied the song of the Lark Sparrow (Chondestes grammacus) in recordings of 15 individuals from a variety of locations in California. Lark Sparrow song is delivered as variable sequences structured in a hierarchy of four levels: elements, syllables, strophes, and themes. At the simplest level, elements can be distinguished by their appearance on a spectrogram. Birds vary the number of repetitions of each element to produce a syllable and string together several syllables to produce a strophe (mean 5.9 syllables per strophe). Strophes are delivered at an average rate of 5.4 per minute. Strophes can be further classified as belonging to one of a few themes in a male's repertoire, where strophes in different themes are composed of almost entirely distinct elements and syllables. In <6% of strophes did we find elements from one theme mixed with elements from a different theme. Each individual sang one to three themes. The size of the repertoire of strophes is large but we could not quantify it because within a continuous bout of singing any particular sequence of syllables was repeated in only 5% of strophes. Each theme comprised roughly 20-40 distinct syllables. Thus an individual singing three themes could have a repertoire of 60-120 syllables. The number of unique elements per theme ranged from 11 in birds revealing just one theme up to 39 in birds revealing three themes, but longer recordings may have yielded more elements per bird. If our observations for single-themed birds may be extrapolated, birds with three themes might have repertoires of 33-51 elements. In the two comparisons possible, we detected almost no sharing of elements among neighboring birds. [ABSTRACT FROM AUTHOR]