In the following we briefly analyze and compare voice of the two races of Olive-brown Oriole (Oriolus melanotis). 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) and Macaulay Library (ML).
We have located recordings of race finschi from Wetar, and of race melanotis from both Timor and Roti. We have measured a number of basic sound parameters and calculated effect sizes:
finschi (n=10): Song often consists of a single loud whistle, which often rises in pitch before dropping. Sometimes whistle is preceded by one or (rarely) a few very short notes.
range Average Standard Dev.
min.freq. 580 - 1600Hz 889Hz 298Hz
max. freq. 2300 - 3150Hz 2821Hz 277Hz
freq. range 1430 - 2500Hz 1930Hz 340Hz
min. phrase length 0.32 - 0.75s 0.50s 0.14s
max. phrase length 0.35 - 0.86s 0.61s 0.25s
shortest note length 0.025 - 0.46s 0.24s 0.19s
longest note length 0.35 - 0.50s 0.44s 0.07s
# notes/phrase 1 - 3 1.7 0.85
melanotis(n=10): Song typically consists of one or a few short notes followed by a slightly longer loud whistle, which typically drops abruptly in pitch about halfway (thus sounding bisyllabic).
range Average Standard Dev.
min.freq. 520 - 960Hz 717Hz 139Hz
max. freq. 1520 - 2500Hz 1906Hz 308Hz
freq. range 850 - 1870Hz 1190Hz 289Hz
min. phrase length 0.52 - 0.98s 0.77s 0.14s
max. phrase length 0.55 - 1.00s 0.80s 0.15s
shortest note length 0.03 - 0.18s 0.10s 0.04s
longest note length 0.24 - 0.54s 0.40s 0.09s
# notes/phrase 2 - 5 3.0 0.9
Main differences in basic parameters are:
effect size score
max. freq. 3.12 2
freq. range 2.35 2
min. phrase length 1.93 1
shortest note length 1.02 1
#notes/phrase 1.49 1
Unlike finschi, song phrase of melanotis apparently never consists of a single long whistle, whistles don't reach as high frequencies as finschi and lack the rather typical (irregular) overslurred shape of finschi , resulting in a smaller frequency range. When applying Tobias criteria, this would lead to a total score of 3-4 (depending whether we consider max. freq. and freq. range independent or not).
This note was finalized on 9th October 2015, 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 and ML: Timothy Burr, Stijn Coleman, Hervé Jacob, Frank Lambert, Mike Nelson, Colin Trainor and Philippe Verbelen.
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: on160_olive-brown_oriole.pdf