In the following we briefly analyze and compare voice of the two races of Short-tailed Green Magpie (Cissa thalassina). 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).
Vocal repertoire of both races is quite extensive, as can be seen from the following overview per race (illustrated with multiple sonograms in the pdf version of this note):
Race thalassina (based on 7 available recordings): a long series of fast repeated identical notes, a short phrase of 4 tinkling notes descending in pitch, often in bursts of 2 or 3 phrases, or a variant, and single notes.
Race jefferyi: a melodious song-like phrase of clear whistles, a double short phrase repeated (possibly of 2 birds responding to each other), and drawn-out harsh grating notes.
Vocabulary of both races is varied, and one can expect that with more recordings a wider repertoire will appear. Nevertheless, from the above examples it is clear that voice of both races shows important differences. Race jefferyi uses much more different and purer whistles leading to complex phrases either given by a single bird or by more birds in asynchronous duet. Also, the fundamental frequency of some of these whistled notes reaches maximum frequencies above 5kHz, while none of the notes in thalassina has fundamental frequencies as high as 5kHz (score at least 2). The long series of repeated notes has not been recorded for jefferyi, despite being the best documented race (score 1). When applying Tobias criteria, this would lead to a total vocal score of at least 3.
Van Balen (2013) used another approach by 'dissecting' the vocalizations into the smallest elements ('motifs'), and by checking which race used these elements to compose their vocalizations. They come to the same conclusion that both races are vocally highly distinct (also in comparison with other members of this genus).
This note was finalized on 26th January 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: Patrik Åberg, Nick Athanas, David Edwards, Richard Hoyer, Frank Lambert, Linda Macaulay, Arnold Meijer, Mike Nelson, Bas van Balen and Arnoud van den Berg.
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.
van Balen, S.(B.), Eaton, J.A. and Rheindt, F.E. (2013). Biology, taxonomy and conservation status of the Short-tailed Green Magpie Cissa [t.] thalassina from Java. Bird Conserv. Int. 23: 91–109.