In the following we briefly analyze and compare voice of Eastern Olive Sunbird (Cyanomitra olivacea) and Western Olive Sunbird (Cyanomitra obscura). 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).
Eastern Olive Sunbird: song is a series of staccato notes, ranging from a simple short descending series to a long series with sequences going up and down in pitch. Some examples (illustrated with multiple sonograms in the pdf version of this note): South Africa, Tanzania and SE Kenya.
Western Olive Sunbird: song is a series of staccato notes, ranging from a simple short descending series to a long series with up and down sequences. Some examples: Ghana, Cameroon and Uganda.
From the above examples, it would seem that song is quite uniform over the entire range of the two groups. At least all basic sound parameters are about equal (note length, # of notes, min/max freq., freq. range...). Even note shapes are very similar. We can only conclude that there are no obvious vocal differences between both groups. A more in depth study may still reveal slight differences in vocabulary, but in any case, this will not lead to high scores for vocal difference.
This note was finalized on 25th April 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.
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: on337_olive_sunbird.pdf