In the following we briefly analyze and compare voice of the different races of Scaly-breasted Wren-babbler (Pnoepyga albiventer). 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).
Voice has already been analyzed in Päckert et al. (2013), concluding that there is a significant vocal difference in frequency and time parameters between Nepal and China populations, the latter being longer in duration and having a narrower frequency range.
As apparently no recordings were analyzed from intermediate regions (Bhutan and NE India), and quite a few recordings are available, we will reassess vocal differences here, which will also allow quantification according to Tobias criteria.
A few examples (illustrated with multiple sonograms in the pdf version of this note): palidior, albiventer and 'mutica'.
From the above, we can deduct that sonograms for Chinese mutica don't show such a striking difference as depicted in Päckert et al. (2013). We can nevertheless deduct that e.g. 3 of the 4 examples from China stay below 6kHz, while all others go above 6kHz. This may be somewhat clinal however: palidior reaches highest frequencies, then albiventer, then 'mutica'. Given that vocal differences are clearly not that straightforward I have made measurements of the basic sound parameters:
max. freq. 6670 - 7400Hz
min. freq. 2370 - 3700Hz
freq. range 3300 - 5000Hz
# elements 12 - 15
total length 1.33 - 1.54s
av. pace (s/element) 0.10 - 0.11
max. freq. 6400 - 7500Hz
min. freq. 2100 - 2900Hz
freq. range 3700 - 4800Hz
# elements 11 - 16
total length 1.53 - 2.07s
av. pace (s/element) 0.11 - 0.14
max. freq. 5450 - 6500Hz
min. freq. 1611 - 2400Hz
freq. range 3100 - 4700Hz
# elements 11 - 16
total length 1.48 - 1.96s
av. pace (s/element) 0.12 - 0.135
It is clear that maximum frequency is the most distinctive parameter for 'mutica'. Minimum frequency is rather clinal between races. All other parameters show less pronounced differences (including frequency range and phrase duration, for which we can't confirm the findings of Päckert et al. (2013)).
We therefore finalize with an effect size calculation of combined palidior/albiventer vs. 'mutica' for maximum frequency:
palidior/albiventer (n=10) av. 6968Hz SD 334Hz
'mutica' (n=4) av. 5762Hz SD 429Hz
-> Effect size 3.13 -> score 2
We can thus conclude that 'mutica' indeed shows some vocal difference compared to palidior/albiventer, but this difference seems to be rather minor and may well be the result of a clinal change from west to east.
This note was finalized on 12th February 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: Nick Athanas, Mike Catsis, Subhajit Chaudhuri, Brian Cox, Niels Poul Dreyer, Peter Ericsson, Frank Lambert, Antero Lindholm, Mike Nelson, Mathias Ritschard, Sudipto Roy, Ante Strand, Joshi Viral and George Wagner.
Päckert, M., Martens, J., Liang, W., Hsu, W.-C. & Sun, Y.-H. (2013). Molecular genetic and bioacoustic differentiation of Pnoepyga wren-babblers. J. Orn.154(2): 329–337.
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: on233_scaly-breasted_wren-babbler.pdf