In the following we briefly analyze and compare voice of the different races of Eyebrowed Wren-babbler (Napothera epilepidota). 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 a single whistle (at constant pitch or slightly descending), repeated at intervals. There seems to be a slight regional difference (illustrated with multiple sonograms in the pdf version of this note):
Birds from Java and Sumatra (epilepidota and diluta) utter a whistle at about constant pitch or at most with initial part descending, and all whistles are clearly shorter than 1 second (n=15).
Birds from N Thailand (davisoni) seem to have the longest whistles (length > 1s), always gradually descending.
Birds from NE India (roberti), China and Vietnam (amyae) have similar, but on average shorter whistles.
Birds of Peninsular Malaysia (granti) surprisingly seem to have a slightly upslurred whistle (n=1).
The Sunda group thus seems to be the most distinctive (and could be given a score based e.g. on 'pitch change in second half of whistle' ). (No recordings from Borneo are available, except for an aberrant recording ML129450).
If the song in Peninsular Malaysia and S Thailand (granti) is indeed upslurred (to be confirmed by more samples), this would also lead to a vocal score of about 3 (e.g. based on 'end freq - start freq')
This note was finalized on 12th 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, ML and AVoCet.
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: on272_eyebrowed_wren-babbler.pdf