Notes on the vocalizations of Short-tailed Antthrush (Chamaeza campanisona)

In the following we briefly analyze and compare voice of the different races of Short-tailed Antthrush (Chamaeza campanisona). 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).

Song of all races is structurally similar, but with clear differences in a number of parameters (Fig. 1). Twelve races are currently recognized, but from a first comparison, it would seem that there are five vocal groups. We have taken measurements for a number of basic sound parameters of the loudsong:

Group 1: Northern Venezuelan mountains (venezuelana)

First part of song       

                # notes                                  13-18

                pace* at start                       0.42-0.47

                pace at end                          0.25-0.275

                max. mid freq.                     930-1040Hz

                max. note length                 0.2-0.215s

Second part of song

                # notes                                  6-9

                freq. drop                             150-380Hz

                note length                          0.16-0.2s

                pace                                      0.344-0.37

Total length                                         7.25-8s

* pace: measured here as period, duration between 2 subsequent notes in seconds.

Group 2: Tepuis of SE Venezuela (presumed obscura)

First part of song

                # notes                                  >50, barely countable at end

                pace at start                         0.34-0.47

                pace at end                          0.074-0.076

                max. mid freq.                     811-880Hz

                max. note length                 0.16-0.2s

Second part of song

                # notes                                  4-7

                freq. drop                             140-220Hz

                note length                          0.14-0.16s

                pace                                      0.35-0.37

Total length                                          9.3-10.3s

 

Group 3: Andes from Colombia to N Peru

First part of song

                # notes                                  21-29

                pace at start                         0.30-0.36

                pace at end                          0.18-0.20

                max. mid freq.                     1050-1120Hz

                max. note length                 0.13-0.15s

Second part of song

                # notes                                  8-12

                freq. drop                             350-480hz

                note length                          0.14-0.18s

                pace                                      0.34-0.39

Total length                                         9.0-11.0s

 

Group 4: Andes from C Peru to Bolivia

First part of song

                # notes                                  48 - >60

                pace at start                         0.15-0.16

                pace at end                          0.09-0.12             

                max. mid freq.                     1100-1180Hz

                max. note length                 0.10-0.11s

Second part of song

                # notes                                  11-22

                freq. drop                             400-420Hz

                note length                          0.09-0.14s

                pace                                      0.17-0.22

Total length                                      9.84-11.65s

 

Group 5: Atlantic Brazil

First part of song

                # notes                                  52 - >80

                pace at start                         0.155-0.21

                pace at end                          0.12-0.15

                max. mid freq.                     1060-1140Hz

                max. note length                 0.095-0.12s

Second part of song

                # notes                                  3-11 (usually just a few, occasionally more)

                freq. drop                             180-400Hz

                note length                          0.05-0.08s

                pace                                      0.12-0.17

Total length                                         8.3-14.5s

 

 

Discussion:

Group 1: Northern Venezuelan mountains (venezuelana) stands apart in many aspects: lowest number of notes, slowest pace at start, slowest pace at end, longest notes and shortest song (even compared to N Andes group) !

Group 2 is unique in having an extreme acceleration (ratio 'pace at start/pace at end') (score 3-4) and having the lowest frequency (score about 2 if more samples confirm this)

Group 3, while less so than group 1, differs from group 4 and 5 in its lower number of notes, slower pace at start and end, and equally so in the second part of the song.

Group 4 and 5 are quite similar, but can still be safely separated by the second part of the song, which is quite different: group 4 has more notes which are longer and delivered at a slower pace (total score approx. 3).

 

If a 5-way separation in groups or species can't be supported by other characters, then clustering group 1 and 3, and group 4 and 5 would result in 3 groups with still clearly defined vocal differences:

 

                                    Group 1 and 3                        Group 4 and 5

                                     combined                                  combined

First part of song       

                # notes                  13-29                                     48 - >80

                pace at start         0.30-0.47                              0.15-0.21             

                pace at end          0.18-0.275                            0.09-0.15

                max. note length 0.13-0.215s                          0.095-0.12s

Second part of song

                note length           0.16-0.2s                               0.05-0.14s           

                pace                       0.344-0.39                            0.12-0.22

 

The clustering of group 4 and 5 seems however somewhat counter-intuitive based on distribution.

 

This note was finalized on 12th June 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.

 

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: on75_short-tailed_antthrush.pdf