Variable or atypical? Comparing unusual songs of the Tufted Titmouse with a citizen-science database

The Tufted Titmouse Baeolophus bicolor is well known for its stereotyped “peter-peter-peter” song, but anecdotal reports of its song’s diversity also exist. We identified an atypical song in East-Central Illinois, USA, that has persisted for several years in the same vicinity. We used a spectrogram-based comparison metric to assess song similarity scores against con- and heterospecific songs from a citizen-science database. The results suggest that these novel songs may truly be outliers beyond the Tufted Titmouse’s local range of species-typical song variability. Our study also illustrates a methodological approach regarding the assessment of other, potentially atypical vocalizations recorded from birds.