In the following we briefly analyze and compare voice of the different races of Thick-billed Grasswren (Amytornis textilis). 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 Macaulay Library (ML).
There are very few recordings available, only of races textilis and modestus. Song of both races starts with a few high-pitched 'tsee' notes which lead to a variable squeaky twittered phrase. The latter consists of several sharply descending or rising notes covering a wide frequency range, and occasionally also includes a fast and short high-pitched rattle.
min freq. 7000 - 7900Hz
max. freq. 8800 - 9000Hz
longest note 0.11 - 0.135s
min freq. 2200 - 3770Hz
max. freq. 13000 - 15600Hz
min freq. 7000 - 7100Hz
max. freq. 8000 - 9000Hz
longest note 0.085 - 0.095s
min freq. 2259 - 3700s
max. freq. 11000 - 13700Hz
From the above, it would seem that there are no obvious differences among both races. There is a possibility that modestus has slightly shorter notes, and reaches slightly lower frequencies, but more samples would be needed to prove this, or any other vocal difference.
This note was finalized on 1st October 2015, using sound recordings available on-line at that moment. We would like to thank in particular the Macaulay Library for giving access to restricted recordings.
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: on149_thick-billed_grasswren.pdf