Notes on the vocalizations of Long-winged Antwren (Myrmotherula longipennis)

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:

longipennis (n=3)

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

 

zimmeri (n=4)

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.

 

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: on48_long-winged_antwren.pdf