Submission Type
Poster
Abstract
Studies show that the White-throated Sparrow's (Zonotrichia albicolis) song is evolving across North America. Previously, most songs ended in a series of "triplets" consisting of three notes. Sometime after the 1960s, a new variant arose in western Canada that ended in a series of "doublets" consisting of two notes. A recent study found that the doublet variant has since spread rapidly eastward across the continent, replacing the triplet variant. We set out to document this shift in southwest Missouri, which is part of the sparrow's wintering range. We found that triplets were significantly more common than doublets, indicating that the new variant is not yet dominant here. Additionally, there was substantial disagreement among observers when attempting to score songs as doublet or triplet. To minimize observer bias, we developed an approach to quantitatively describe rhythmic variants. We sourced song recordings from sound repositories and isolated the last series of notes. Because these notes typically have a constant frequency, we were able to remove background noise with customized bandpass filters based on the recording's peak frequency. We then determined the onset time of each note in the series from amplitude profiles. Using the intervals between these onsets, we calculated a numerical score for each song corresponding to its degree of doublet patterning. This quantitative, repeatable approach will enable new analyses of rhythm variation and evolution in White-throated Sparrow songs.
Key Words: bioacoustics, ornithology, bird song, cultural evolution, Passeriformes
Included in
A novel approach to scoring rhythmic variation in evolving White-throated Sparrow (Zonotrichia albicolis) songs
Studies show that the White-throated Sparrow's (Zonotrichia albicolis) song is evolving across North America. Previously, most songs ended in a series of "triplets" consisting of three notes. Sometime after the 1960s, a new variant arose in western Canada that ended in a series of "doublets" consisting of two notes. A recent study found that the doublet variant has since spread rapidly eastward across the continent, replacing the triplet variant. We set out to document this shift in southwest Missouri, which is part of the sparrow's wintering range. We found that triplets were significantly more common than doublets, indicating that the new variant is not yet dominant here. Additionally, there was substantial disagreement among observers when attempting to score songs as doublet or triplet. To minimize observer bias, we developed an approach to quantitatively describe rhythmic variants. We sourced song recordings from sound repositories and isolated the last series of notes. Because these notes typically have a constant frequency, we were able to remove background noise with customized bandpass filters based on the recording's peak frequency. We then determined the onset time of each note in the series from amplitude profiles. Using the intervals between these onsets, we calculated a numerical score for each song corresponding to its degree of doublet patterning. This quantitative, repeatable approach will enable new analyses of rhythm variation and evolution in White-throated Sparrow songs.
Key Words: bioacoustics, ornithology, bird song, cultural evolution, Passeriformes
Comments
Shelby Palmer (Missouri State University), Rachel Lange (no affiliated institution), Dan Zapata (University of Windsor), Jay McEntee (Missouri State University)