In the following we briefly analyze and compare voice of the different races of Wedge-tailed Grass-finch (Emberizoides herbicola). 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 Macaulay Library (ML).
An overview of song per region (illustrated with multiple sonograms in the pdf version of this note): Panama (n=1), Northern S America (S Ecuador, N Peru, Colombia, SE Venezuela, French Guyana), Southern S America (Bolivia, S Brazil).
Northern S America group (excl. S Ecuador/N Peru and NE Brazil) typically has a song starting with one or a few "pit" notes followed by 2-3 short complex notes, of which usually 2 are about identical. "pt..pit..tchip..chee.cheew".
Southern S America group (and S Ecuador/N Peru) typically has a song which is quite variable, but always contains 1 or 2 complex notes with clearly slurred parts and without any repeats.
Vocally it would thus seem that the population in S Ecuador and N Peru (which is supposed to be part of sphenurus) rather fits herbicola ! In the same way, birds from Belem area (S of the Amazon) fit herbicola, not sphenurus.
There is thus vocally a clear dividing line by the river Amazon.
Vocal differences can be quantified as follows: Southern group lacks any repeats (score 2) and has the longest slurred notes (score 2). Total score about 4.
We have only a single recording of Central America, consisting of an introductory "pit" note followed by a short complex note repeated 2-3 times (sometimes 2+3 in one phrase). Based on a single recording of Central American races, little can be said about vocal difference vs Northern S America group, but it would seem that identical repetitions of a single note are even more pronounced here (Panama).
This note was finalized on 2nd July 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: on397_wedge-tailed_grass-finch.pdf