In the following we briefly analyze and compare voice of the different races of Slaty-backed Chat-tyrant (Ochthoeca cinnamomeiventris). 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).
Day-time song is a high-pitched whistle. When agitated this high-pitched whistle is followed by a series of notes. In the following we only compare the single high-pitched whistle (Fig. 1, illustrated in the pdf verion of this note):
O. c. cinnamomeiventris (n=9)
min. freq. 3900-5000Hz
max. freq. 5800-7900Hz
freq. range 2000-3500Hz
total length 0.54-0.86s
note shape crescent-shaped, usually with some artefacts at start, and sometimes quite buzzy
O. c. angustifasciata and O. c. thoracica (n=7)
min. freq. 4700-6400Hz
max. freq. 5900-8300Hz
freq. range 600-1900Hz
total length 0.90-1.22s
note shape initially rising, then usually gradually descending
O. c. nigrita (0 recordings available)
The whistled note of O. c. angustifasciata/thoracica clearly differs by its longer length (score 2), smaller frequency range (score 2) and slightly higher lowest frequency (score 1). When applying Tobias criteria, this would lead to a total vocal score of 4.
Hilty (2003) decribes nigrita and cinnamomeiventris as two distinct species in his Venezuela guide, with voice descriptions that clearly indicate a difference. We haven't found any recordings to substantiate this difference, and unfortunately Hilty's (analog) recordings were not readily available (in litt.). We can thus only conclude there is probably also a vocal difference here.
This note was finalized on 10th July 2015, 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.L. (2003). Birds of Venezuela. Princeton University Press & Christopher Helm, Princeton & 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: on253_slaty-backed_chat-tyrant.pdf