In the following we briefly analyze and compare voice of the different races of Blue-black Grosbeak (Cyanocompsa cyanoides). 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).
A comparison of song of the different races (illustrated with multiple sonograms in the pdf version of this note): rotschildii (E and S Venezuela, Guianas, SW Amazon), cyanoides, caerulescens, concreta.
Differences in song are rather subtle. rotschildi has typically a song consisting of some 6-7 melancholic notes, rather flat in pitch, the series gradually descending in pitch. Second part of the song is quite variable. cyanoides and caerulescens have a song which is similar, but notes are less flat-pitched, typically with more alternating note shapes (e.g. upslurred and downslurred). Rather diagnostic is the longer pause between first and second note. This is less so in concreta. concreta and caerulescens also reach somewhat lower frequencies.
Recordings from N Venezuela (Falcón and Carabobo) do not fit rotschildi, and we assume here these are actually cyanoides, as stated in Hilty (2003).
All in all, we can conclude that rotschildi is vocally slightly different, with notes typically flatter-pitched (1) and without a clear pause after the first note (1). Total vocal score 2.
This note was finalized on 29th June 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.
Hilty, S. (2003). Birds of Venezuela. Helm Field Guides. Christopher Helm, London.
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: on385_blue-black_grosbeak.pdf