In the following we briefly analyze and compare voice of the different races of Forest Robin (Stiphrornis erythrothorax). 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).
A comparison of typical song phrases per race (illustrated with mutiple sonograms in the pdf version of this note): erytrothorax, gabonensis, xanthogaster. (sanghensis: no recordings available, S. pyrrholaemus: no recordings available).
From the above examples it is clear that song of xanthogaster is very different: a phrase of very short pure notes which go up and down in pitch creating a slowly oscillating song phrase. This song phrase can be relatively short (c. 2s) repeated at intervals, but more commonly is long or very long (>10s). Descriptions for song of sanghensis seem to indicate a similar song (HBW Alive: Collar 2016, Clement 2015).
Main differences with song of erythrotorax and gabonensis are thus a higher number (score 2-3) of shorter notes (score 2) in longer song phrases (2). When applying Tobias criteria, this would lead to a total vocal score of about 4.
Song of erythrotorax and gabonensis is less strikingly different: erythrotorax has mainly short song phrases (1 - 1.2s) consisting of about 5 notes in a narrow frequency range (c. 1.5kHz). gabonensis has more loose song phrases without much difference between inter-note spaces and inter-phrase spacing (2). Notes slightly longer and typically flat-pitched (1). Freq. range somewhat variable.
This note was finalized on 10th May 2016, 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: Sander Bot, Jacob Cooper, Brian Cox, Hans Groot, Peter Kaestner, Frank Lambert, Etienne Leroy, Carolyn McBride, David Moyer, Bram Piot, Mark Robbins, Paul Rodewald, Martin St-Michel, Keith Stuart and Crammy Wanyama.
Clement, P. & Rose, C.(2015). Robins and Chats. Helm identification guides. Christopher Helm, London.
Collar, N. (2016). Forest Robin (Stiphrornis erythrothorax). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/58428 on 10 May 2016).
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: on321_forest_robin.pdf