RANGEWIDE VARIATION IN THE SONG OF SEASIDE SPARROWS (AMMOSPIZA MARITIMA)
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Abstract
Acoustic communication is a well-studied behavior in many avian species. Bird song, used for defending territory or as a mating signal, is particularly well studied within avian vocalization. Variation within song between populations or individuals has been described in many species. In some instances, particular variations in song can be used to distinguish between populations or subspecies. The Seaside Sparrow (Ammospiza maritima) is a saltmarsh obligate songbird whose range is restricted to coastal saltmarsh habitat along the Atlantic and Gulf coasts of North America. There are six currently recognized subspecies of Seaside Sparrow, and audio records exist from a seventh but extinct subspecies of Seaside Sparrow. Additionally, mtDNA has been used to group these seven subspecies into the Atlantic and Gulf coastal lineages, which are hypothesized to have diverged up to 500,000 years. Here, I investigate whether Seaside Sparrow song can be distinguished at two scales (subspecies and coastal lineage) using overall song structure or syllable composition. I examined whether variation in the song of Seaside Sparrows aligns with current subspecific taxonomy and if patterns in syllable inclusion, composition of first phrase, or the duration and frequency range of seven measured song components could be used to differentiate subspecies or coastal lineage of the Seaside Sparrow. Although song components do not correlate with Seaside Sparrow subspecies designation, a linear model based on a subset of song components was able to assign coastal lineage with ~81.5% accuracy. Approximately 91% of songs possessed unique syllable composition within the first phrase of the Seaside Sparrows song. Syllable accumulation curves show differences between subspecies in syllable diversity in sample sizes greater than 80 songs. Syllables and first phrase composition were unable to accurately assign subspecies or coastal lineage. These findings suggest that variation in song components within the song of the Seaside Sparrow are more closely aligned with coastal lineage than subspecies designation.