In the following we briefly analyze and compare voice of the different races of Pale-breasted Illadopsis (Illadopsis rufipennis). 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).
Song is very similar to some other members of the genus such as Brown Illadopsis I. fulvescens: a combination of long whistles at constant pitch and a few much shorter notes. Pitch may vary somewhat, and number of short notes as well. All races (except distans) are vocally about the same. Some examples (illustrated by multiple sonograms in the pdf version of this note): Ghana, Cameroon and Kenya.
Song of race distans from NE Tanzania is very different, namely short phrases of different slurred whistles, without any longer whistles at constant pitch.
This confirms earlier indications that distans has a different voice (Zimmerman et al. 1996)
This vocal difference can easily be quantified by parameters such as e.g. frequency range of notes, longest note length, average number of notes per phrase, maximum length ratio between different notes etc. While there are only a few recordings available of race distans, we estimate that measurement of these sound parameters on a larger set of samples would lead to a total vocal score of about 3+3 = 6
This note was finalized on 11th April 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 and ML: Mikael Bauer, Sander Bot, James Bradley, Mike Catsis, Jacob Cooper, Louis Hansen, Linda Macaulay, Carolyn McBride, David Moyer, Mike Nelson, Mark Robbins, Paul Rodewald and Keith Stuart.
Zimmerman, D.A., Turner, D.A. & Pearson, D.J. (1996). Birds of Kenya and Northern Tanzania. Helm Identification Guides. Christopher Helm, London.
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: on268_pale-breasted_illadopsis.pdf