Notes on the vocalizations of Rufous-fronted Thornbird (Phacellodomus rufifrons)

In the following we briefly analyze and compare voice of the different races of Rufous-fronted Thornbird (Phacellodomus rufifrons). 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).

Song is similar to several other members of the genus, a loud series of nearly-identical staccato notes. In typical song of a single individual, series starts with well-spaced notes, slowly accelerating, intensifying and increasing in pitch, then slowing, decreasing and fading. Often however, at least two birds sing together, and when excited, deliver very long series of nearly-identical notes, at some point ending abruptly.

When comparing inornatus/castilloi with all other races, it is quickly obvious that song is much higher-pitched. We have therefore measured all basic parameters in a number of recordings, in order to quantify differences:

inornatus/castilloi (n=7)

Max. freq.                                                            4450-4900Hz

Min freq.                                                              950-1150Hz

Freq. range of single note                                 3050-3900Hz

Note length                                                         0.05-0.07s           

# notes to reach max pitch                               4-6 (only measured for typical rising/falling songs)

song length                                                          2.4-3.08s (idem)

# of notes                                                            15-19 (idem)

pace*                                                                   0.13-0.19

 

peruvianus (n=3)

Max. freq.                                                            1680-2200Hz

Min freq.                                                              650-850Hz

Freq. range of single note                                 900-1500Hz

Note length                                                         0.075-0.11s

# notes to reach max pitch                               6 (only measured for typical rising/falling songs)

song length                                                          3.4s

# of notes                                                            15

pace                                                                      0.23

 

sincipitalis (n=3 )

Max. freq.                                                            2000-2100Hz

Min freq.                                                              800-1000Hz

Freq. range of single note                                 1200-1250Hz

Note length                                                         0.07-0.115s         

# notes to reach max pitch                               4-5 (only measured for typical rising/falling songs)

song length                                                          6.4-8s

# of notes                                                            27-32

pace                                                                      0.23-0.25

 

specularis/rufifrons (n=5)

Max. freq.                                                            1650-3400Hz

Min freq.                                                              680-1140Hz

Freq. range of single note                                 900-2250Hz

Note length                                                         0.05-0.10             

# notes to reach max pitch                               4-6 (only measured for typical rising/falling songs)

song length                                                          1.9-9.5s

# of notes                                                             14-76                                   

pace                                                                       0.13-0.17                                     

* pace measured here as period: duration of note + pause

 

There seem to be three vocally different groups. The largest difference is between inornatus/castilloi and peruvianus/sincipitalis, as the former has clearly higher max. freq. (score 3) with weaker harmonics and notes with a high frequency range (score 2), shorter note lengths (score 1) and a faster pace of delivery (score 2). This would lead to a total vocal score of about 5 when applying Tobias criteria.​ specularis/rufifrons shares the low frequency with peruvianus/sincipitalis, but the faster pace with inornatus/castilloi.

If inornatus/castilloi has to be compared with all others in one single enlarged group, then only the higher max. freq. and frequency range remain, leading to a total score of 4 or 5.

 

This note was finalized on 16th April 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.

 

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: on95_rufous-fronted_thornbird.pdf