In the following we briefly analyze and compare voice of the two races of Bridled White-eye (Zosterops conspicillatus). 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).
Vocabulary seems to be quite varied. An overview of vocalizations based on the available recordings (illustrated with multiple examples in the pdf version of this note):
saypani: medium-pitched chirps, low-pitched chirps, high-pitched notes, nasal notes and song-like high-pitched phrases
conspicillatus (Guam, n=4): There are few recordings available of nominate, and this is unlikely to change given that this taxon is presumably extinct. Buzzy notes and high-pitched notes (if those are of the White-eye ??)
It would thus seem that vocabulary is rather distinct, saypani lacking the buzzy notes which are seemingly typical for conspicillatus. For comparison, we also include recordings from Yap: H. hypolais : Sparrow-like downslurred chirps, rattles, plaintive, burry notes and sparrow-like upslurred chirps. Vocabulary of these three taxa is thus clearly distinct.
Vocal differences were already noted in HBW (van Balen 2016): Song of nominate race a lilting series of buzzy notes, “zeeip-zee-zee-zoo-zip”, and calls a buzzy chirp “cheep” or “tszeeip”, lacking high-pitched calls of saypani. Race saypani has higher-pitched, less buzzy calls, with chirps often rapidly uttered and organized into loose song; “confusion” chorus described. Calls of both races, especially in flight, sound like those of House Sparrow (Passer domesticus); in flocks a series of “chit-chit” notes, and whining vocalizations, which used also in agonistic interactions.
These differences can be confirmed to a large extent by the above sonogram examples. Quantifying differences is not straightforward given that it is not clear which are homologous calls. It is however clear that saypani has a more extensive vocabulary (2), including several high-pitched call notes unlike nominate (2) and lacking notes with a distinct buzzy sound quality (2). In absence of a clear set of homologous vocalizations, we estimate the total vocal score to be about 4.
This note was finalized on 28th June 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: James Bradley and (especially) Douglas Pratt.
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, B. (2016). Bridled White-eye (Zosterops conspicillatus). In: del Hoyo, J., Elliott, A., Sargatal, J., Christie, D.A. & de Juana, E. (eds.). Handbook of the Birds of the World Alive. Lynx Edicions, Barcelona. (retrieved from http://www.hbw.com/node/60166 on 28 June 2016).
More Information: on263_bridled_white-eye.pdf