In the following we briefly analyze and compare voice of the different races of Long-winged Antwren (Myrmotherula longipennis). 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).
Loudsong of Long-winged Antwren is a short series of whistled notes. There are however clear differences in song between the various races.
It should be noted however that e.g. song of races from SE Peru to E Brazil show a rather gradual change in voice. Or when looking at all races, it would seem that starting with longipennis and going counterclockwise through the Amazon region every next race has some difference with the previous and the next race, a gradual change which leads to a completely different song between longipennis and paraensis, suggesting somewhat an evolution as a ring species.
While longipennis has a series of gently rising whistles at roughly the same pitch, this changes step-wise to a rising series of notably under-slurred whistles, shorter in length and delivered at a higher pace in paraensis.
It is thus not at all straightforward to cluster the 6 races into a two or more groups.
As an example, some measurements of loudsong of longipennis and zimmeri, which sound quite different:
A series of burry slightly rising whistles at roughly the same pitch (or slightly decreasing) over its entire length.
initial freq. first note 3200-3600Hz
end freq. first note 3900-4500Hz
freq. increase first note 600-900Hz
frequency range first note 800-1000Hz
initial freq. last note 3000-3200Hz
end freq. last note 3600-3900Hz
freq. increase last note 600-800Hz
frequency range last note 800-1000Hz
overall frequency range 1300-1600Hz
length first note 0.5-0.65s
length last note 0.4-0.5s
total pace 0.62-0.83
note shape slightly rising in pitch, lowest frequency at start
A series of slightly burry under-slurred whistles gradually increasing in pitch
initial freq. first note 2900-3400Hz
end freq. first note 4300-4400Hz
freq. increase first note 1000-1500Hz
frequency range first note 2000-2700Hz
initial freq. last note 4500-4800Hz
end freq. last note 4600-5300Hz
freq. increase last note 0-600Hz
frequency range last note 1600-1800Hz
overall frequency range 2200-3500Hz
length first note 0.43-0.56s
length last note 0.36-0.47s
total pace 0.6-0.75
note shape under-slurred, lowest frequency halfway note length
It is clear that there are several frequency-related variables which are different, the most obvious being the overall frequency range (score 2 or 3). Other independent parameters are less obvious and could at most reach a score 1 (e.g. note shape). This leads to a total score of 2-4.
It is to be expected that side by side comparison of all races will lead to scores in this range (or less). Obviously, when comparing the two extremes, longipennis with paraensis, score would be about 3+3=6, reaching almost species-level differences.
All in all, we can conclude that every race shows minor vocal differences with adjacent races, leading to important vocal differences at the two extremes.
This note was finalized on 5th May 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: Peter Boesman, Tayler Brooks, Sidney de Melo Dantas, Patrick Ingremeau, Niels Krabbe, Dan Lane, Alexander Lees, Mitch Leisinger, Gabriel Leite, Curtis Marantz, Jeremy Minns, John V. Moore, Jonas Nilsson, Otte Ottema, Mark Robbins, Eduardo Patrial, Alexandre Renaudier, Andrew Spencer, Joseph Tobias and Nathalie Seddon.
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: on48_long-winged_antwren.pdf