In the following we briefly analyze and compare voice of the two races of Ryukyu Robin (Luscinia komadori). 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).
A comparison of vocalizations of both races (illustrated with multiple sonograms in the pdf version of this note):
komadori: Song is quite variable but very often starts with one or two rather low-pitched notes at flat pitch, and second part of song typically has a frequency range (bandwidth) of c 3kHz. Commonest call note seems to be a high-pitched slightly rising drawn-out note. A second call, which is occasionally heard, is a low-pitched subdued "drrrr". All recordings are from Amami Island, there may be vocal differences with birds of the same race from other islands.
namiyei: Song is quite variable but very often starts with one or a few high-pitched notes, and second part of song may have a large frequency range (from c 3 to c 7kHz). Commonest call note (8 recordings out of 20 recordings on XC, others being song) is a short rising rattle, given single, in pairs or triples. A second call is a high-pitched "tseeee", which is shorter than in komadori (Chikara 2013).
There are thus some clear vocal differences.
Song: average pitch of introductory notes is low in komadori and high in namiyei (score 2-3). Frequency range of komadori is smaller, even if we exclude the introductory notes, sounding somewhat mellower to the ear (score 1-2).
Call: If we assume the high-pitched notes and the more gravelly/rattling notes are both respectively homologous vocalizations for the two races, then high-pitched notes in namiyei slightly shorter (score 1) and rising rattling note of the latter very different with wide freq. range compared to subdued gravelly call of komadori (score 2), and frequency of delivery of both call types very different.
When applying Tobias criteria, this would lead to a total vocal score of about 4.
This note was finalized on 15th 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: Peter Boesman, Ross Gallardy, Ken Ishida, Frank Lambert, Yann Muzika, Brendan Sloan and Ding Li Yong.
Chikara, O. (2013). The distinction between the two forms of Ryukyu Robin Luscinia komadori komadori and Luscinia komadori namiyei. BirdingASIA 19: 89–91.
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: on325_ryukyu_robin.pdf