Notes on the vocalizations of Red-legged Thrush (Turdus plumbeus)

In the following we briefly analyze and compare voice of the different races of Red-legged Thrush (Turdus plumbeus). 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), Macaulay Library (ML), Avian Vocalizations Center (AVoCet) and The Internet Bird Collection (IBC).

An overview of song per race (illustrated with multiple sonograms in the pdf version of this note): Bahamas (plumbeus), Puerto Rico (ardosiaceus), Dominican Republic (ardosiaceus), Cuba (rubripes/schistaceus).

There are no recordings available of albiventris (Dominica).

There is a slight vocal difference between ardosiaceus (Hispaniola/Puerto Rico) and other races (Cuba/Bahamas): ardosiaceus alternates 1-3 fairly melodious whistles at lower pitch with 1-2 high-pitched notes. Other races have a similar alternating series of notes, but the lower-pitched notes are not at all melodious, rather squeaky (which can be seen from the large freq. range they cover, or  loud harmonics or non-harmonic frequency bands). There is however some overlap, especially birds of Bahamas (plumbeus) are rather intermediate. This could be given a vocal score of 1 (smaller freq. range of low-pitched notes and/or lack of loud harmonics for ardosiaceus).

A more thorough analysis would be required to find out if vocabulary of notes is distinct among races, but a larger set of recordings would be needed to perform such analysis.

This note was finalized on 20th 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.

References

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: on310_red-legged_thrush.pdf