In the following we briefly analyze and compare voice of the different races of Golden-bellied Gerygone (Gerygone sulphurea). 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).
Typical song is a phrase of leisurely delivered wheezy whistles repeated several times. Either, the song phrase is a descending series of whistles, or is going up and down. It would seem that variation within races is as high as among races, which is illustrated by a series of sonograms:
G.s.sulphurea: some typical examples from Thailand, Malaysia and Java (max. freq. 6000-700Hz, min. freq. 2600 - 3000Hz)
G.s. muscicapa (n=1): no obvious differences compared with nominate:
G.s.simplex(n=5): All recordings have the leisurely delivered wheezy whistles, but include some pure short whistles (which are slightly lower-pitched) resulting in a more rhythmic cadence. Some examples of nominate do have some short pure whistles, but never as consistent as here.
G.s.rhizophorae(n=1): no obvious differences compared with nominate.
G.s.flaveola(n=6): 5 of the 7 recordings are of a steadily repeated descending series of wheezy whistles with a clear acceleration after the first notes, unlike other races. 2 recordings from N Sulawesi are of the 'classic sulphurea song'. Certain recordings of race sulphurea do however come close, e.g. Thailand.
From the above, it would seem that basic sound parameters do not differ much if at all, but certain song patterns are more common in certain races. Despite the existing overlap in characters, there are on average clear differences:
simplex typically has a song of wheezy whistles combined with short pure lower-pitched whistles, resulting in a rhythmic cadence (allow score 1-2 vs. all other races).
flaveola typically has a song starting with 1 or 2 long wheezy whistles followed by an accelerating descending series of whistles (allow score 1-2 vs. all other races).
This note was finalized on 7th October 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 and ML: Desmond Allen, Paulo Alves, Peter Boesman, Timothy Burr, David Farrow, Romeo Galang, Ross Gallardy, Robert Kennedy, Doug Knapp, Frank Lambert, Tero Linjama, Mike Nelson 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: on154_golden-bellied_gerygone.pdf