In the following we briefly analyze and compare voice of the different races of Indigo Flycatcher (Eumyias indigo). 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), Macaulay Library (ML) and Avian Vocalizations Center (AVoCet).
Song is similar to other members of the genus, a long series of short sweet whistles, without much variation in pitch, thus sounding rather monotonous. A comparison of song per race (illustrated with multiple sonograms in the pdf version of this note): Borneo (cerviniventris), Java (indigo) and Sumatra (ruficrissa).
Given there is quite a bit of variability, there are no clear differences in song between birds from Borneo and Java.
We have only located two recordings from Sumatra, which suggest also quite some variability, ranging from rather short song strophes with a wider frequency range to long song strophes much more similar to the other two races. More recordings are clearly needed to make a more detailed comparison.
Based on the available recordings, we haven't found clear vocal differneces.
This note was finalized on 8th May 2016, using sound recordings available on-line at that moment. We would like to thank in particular the sound recordists who placed their recordings for this species on XC, ML and AVoCet: Paulo Alves, David Edwards, Richard Hoyer, Ben King, Frank Lambert, Linda Macaulay, Arnold Meijer, Mike Nelson, Pamela Rasmussen, Filip Verbelen and Arnoud van den Berg.
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: on320_indigo_flycatcher.pdf