In the following we briefly analyze and compare voice of the two races of Scarlet-rumped Cacique (Cacicus microrhynchus). 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).
Both races typically emit well-spaced single whistles and much faster rattling series of notes. A comparison of song-like vocalizations (illustrated with multiple sonograms in the pdf version of this note): Race pacificus and nominate (Honduras, Costa Rica and Panama).
Vocal difference between the two races is quite obvious in all homologous vocalizations:
* single notes: nominate utters irregularly overslurred notes reaching max. frequency of 3.2 - 4kHz, pacificus principally downslurred notes reaching max. frequency of 2.2 - 2.6kHz.
* fast rattling series: A similar difference in max. frequency and nominate often combines two series of different repeated notes.
Based on nominate's much higher max. frequency (score 2-3) and different note shape (irregularly overslurred vs principally downslurred)(score 1), application of Tobias criteria would lead to a total vocal score of 3-4.
More recordings are desirable from Colombia and eastern Panama, to have a better understanding of vocal change in the area of contact.
This note was finalized on 24th 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.
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: on369_scarlet-rumped_cacique.pdf