In the following we briefly analyze and compare voice of the three races of Sunda Cuckoo-shrike (Coracina larvata). 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).
We haven't found any recordings of melanocephala (Sumatra), and only a few of other races. We compare here the typical long call of both races (illustrated with sonograms in the pdf version of this note):
From these few samples, it would seem that calls are very constant within each race, and quite distinct among the 2 races.
normani utters typically single calls at a fairly stable pitch over most of its duration. Note shape has a very steep pitch rise at start and pitch drop at end.
larvata utters typically double notes with a distinct peak of max. frequency in every note, and a rather gradual pitch increase/decrease towards those peaks.
This vocal difference, if confirmed by more samples, could be quantified based on # of notes (3), duration of total call (3) and note shape (1). Using Tobias criteria as a guidance, this would lead to an estimated total vocal score of at least 4.
This note was finalized on 4th November 2015, 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: Nick Athanas, Linda Macaulay, Mike Nelson, Pamela Rasmussen, Bas Van Balen, Arnoud Van den Berg, Paul Van Els and Sam Woods.
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: on177_sunda_cuckoo-shrike.pdf