Even birds speak different dialects: How different are they?

Hein, Lewis W.
Birdsong is known to be variable geographically in many species, and we have anecdotally observed this effect in Wyoming populations of the House Wren (Troglodytes aedon). This variation may be due to gradual divergence in song dialects between geographically distinct breeding populations, genetic variation among populations, or habitat-driven differentiation based on sound transmission properties of the environment. In this project, we collected 944 wren calls from three different locations around Wyoming, tested the similarity of various acoustic environments and modeled call similarity against distance and acoustic environment type. These comparisons were made using time-frequency analysis, clustering, and summary statistics. The geographic distribution of these song dialects is shown to be quite diverse, with some locations showing great consistency and others showing as much internal dialect variability as exists between locations. We found that between locations dialects can be distinguished by differences in rate of singing, minimum pitch attained, and the proportion of the song spent in pauses between phrases. These findings may help answer important questions about population diversity, boundaries for mating, and migration patterns.
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