In the following we briefly analyze and compare voice of the two races of Dusky Bush-tanager (Chlorospingus semifuscus). We also try to quantify the extent of any vocal differences using the criteria proposed by Tobias et al. (2010), as a support for taxonomic review. We have made use of sound recordings available on-line from Xeno Canto (XC), and recordings of song of northern race livingstoni were kindly provided by Johnnier Arango-Bermúdez.
Song of both races is a repeated single high-pitched note. A comparison (illustrated with multiple sonograms in the pdf version of this note): livingstoni and nominate.
Song of both races is similar in structure and pace. Given this very simple song, we should thus focus on the single note. In nominate this single note typically is an 'upside down sharp V', with usually main emphasis on the downslurred part. Max. frequency typically 10-11kHz. Note shape of livingstoni is apparently quite different, rather an irregular upslurred note (which has not been found amidst the more numerous recordings of nominate).
We should be aware that this is based on just two individuals of race livingstoni, but given we have many more recordings of nominate, it seems likely that both races have indeed a somewhat different note in their song: livingstoni an irregular upslurred note, nominate an 'upside down sharp V'. If this is confirmed by more recordings, this can be considered a rather significant vocal difference.
This note was finalized on 28th October 2016, using sound recordings available on-line at that moment. We would like to thank in particular the many sound recordists who placed their recordings for this species on XC, and Johnnier Arango-Bermúdez for the sole recordings of race livingstoni.
Tobias, J.A., Seddon, N., Spottiswoode, C.N., Pilgrim, J.D., Fishpool, L.D.C. & Collar, N.J. (2010). Quantitative criteria for species delimitation. Ibis 152(4): 724–746.
More Information: on445_dusky_bush-tanager.pdf