In the following we briefly analyze and compare voice of the different races of Grey Elaenia (Myiopagis caniceps). 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).
Voice is quite varied, and the main song-like vocalizations are a series of fairly high-pitched notes, trailing off into a descending trill, and an excited “e-e-e-e-pitchew pitchew-peechew”, similar in tone quality. The latter is heard less often, and sometimes the trill changes prematurely into (part of) the second vocalization. In the following we only analyze the 'pure and complete' first vocalization to allow for comparison. (We are thus quite selective in our choice, which may reduce the variability and over-emphasize differences)
At first sight, there is little difference in the voice of the different races, but further analysis shows some distinct features:
M. c. parambae (n=6)
max. freq. 5980-7040Hz
start freq. trill 5250-6080Hz
end freq. trill 3900-5200Hz
start note length 0.12-0.155s
end note length 0.05-0.095s
start pace 0.13-0.16
end pace 0.07-0.12
total # notes 11-24
note shape few spaced curly notes followed by trill of sharp dagger-shaped notes
M. c. cinerea (n=5) Cristalino recording Fr. Guyana
max. freq. 5600-7320Hz 7150Hz 5920Hz
start freq. trill 5500-5940Hz 5770Hz 5600Hz
end freq. trill 3800-4870Hz 4100Hz 5300Hz
start note length 0.09-0.10s 0.13s 018s
end note length 0.09-0.10s 0.08s 0.07s
start pace 0.11-0.13 0.15 0.18
end pace 0.11-0.13 0.11 0.11
total # notes 21-31 29 21
note shape few fast sharp notes followed by rounded knife-shaped notes
M. c. caniceps(n=5)
max. freq. 5350-5860Hz
start freq. trill 4950-5860Hz
end freq. trill 4250-5100Hz
start note length 0.095-0.14s
end note length 0.04-0.045s
start pace 0.10-0.16
end pace 0.05-0.06
total # notes 41-69
note shape few overslurred notes followed by trill of overslurred notes
M. c. parambae has the lowest number of notes, has the longest initial notes and has a peculiar note shape readily identified on sonogram.
M. c. cinerea has short initial note length and long end note length, with hardly any change in pace over the trill.
M. c. caniceps has very short end notes, a fast end pace and a strong acceleration in pace. Also the highest number of notes (when considering only 'full trills').
Recordings from Cristalino (extreme N Mato Grosso) fit well within the western Amazonian vocal group (cinerea). A single recording from French Guyana (XC23044) is somewhat more divergent (possibly a different taxon?) but fits best with cinerea.
If we compare caniceps versus the others, we can score based on fast end pace and pace acceleration (score 2) and number of notes (2-3). When applying Tobias criteria, this would result in a total vocal score of 4-5. And when comparing parambae vs. cinerea, the former has fewer notes (score 2), has a different note shape of both introductory notes and trilled notes (score 1-2), and introductory notes are well-spaced (unlike cinerea)(score 2-3). This would lead to a total vocal score of about 4.
Remains to check whether Panamanian race absita is close to parambae. There is only 1 recording of song available from Panama, from the Canal zone (ML105069, there noted as call), which starts with a few spaced curly notes, followed by accelerating dagger-shaped notes, indeed very much like parambae.
We haven't analyzed call notes, which may reveal additional vocal differences. As it is not always clear in what context the calls are given, this poses some extra challenges (some calls are actually just the introductory notes of the song (without the trill), others are different). From a quick scan however, it looks like caniceps has mainly a round overslurred note, cinerea a bisyllabic or double note, and parambae a curly note.
We can thus conclude, that based on comparison of typical song, there are clearly 3 vocal groups, which show significant differences (scores 4-5).
This note was finalized on 21th August 2015, using sound recordings available on-line at that moment. We would like to thank in particular the many sound recordists who placed their recordings for this species on XC and ML.
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: on135_grey_elaenia.pdf