In the following we briefly analyze and compare voice of the different races of Striped Woodhaunter (Hyloctistes subulatus). 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).
It is clear from listening (and looking to sonograms) that vocally all races fall into just two very distinct groups. Out of the ones we looked at (>30), we have taken a limited number of samples (5 of each group) to take measurements and quantify the differences:
W of Andes (H. s. nicaraguae H. s. virgatus H. s. assimilis H. s. cordobae : Song is a series of evenly spaced identical short staccato notes 'keek..keek..keek..keek'.
Number of notes: 3-8 (average about 5), sometimes longer series of >10
Max. length note: 0.04-0.08s
Peak. freq.* of notes: 3750-4650Hz
(* Peak frequency is here defined as the frequency with the highest energy level)
E of Andes (H. s. subulatus, H. s. lemae (n=1, if identification of XC9164 is correct)): Song is a series of just a few (usually 2 or 3) downslurred notes, often (when excited?) followed by a low-pitched rattle.
Number of notes: 2-3 (+ occasionally rattle)
Max length note: 0.22-0.27s
Peak. freq. of notes: 1780-2400Hz
The note shape of both groups is quite similar as is the fundamental frequency (confirming to a certain extent their close relationship). However, W of Andes note length is much shorter and the second harmonic is much louder than the fundamental frequency, the reverse of birds E of Andes, leading to a peak-frequency in a completely different range.
Song of 'western group' differs from 'eastern group' by the higher number of notes (score 1-2), which are shorter in duration (score 3) and have a peak-frequency twice as high (score 2 or 3). Song also lacks the occasional ending rattle as in 'eastern group'. This leads to a total vocal score of 5 or 6 when applying Tobias criteria.
This note was finalized on 17th April 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.
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: on90_striped_woodhaunter.pdf