Notes on the vocalizations of Striated Antbird (Drymophila devillei)

In the following we briefly analyze and compare voice of the different races of Striated Antbird (Drymophila devillei). 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).

A quick look at the sonograms of loudsong indicates there are vocal differences, but these are not necessarily linked to subspecies. We have measured a number of basic sound parameters for several groups. Within the subspecies devillei we can discern several vocally distinctive populations, which lead us to the following groups examined: 

 

devillei from Colombia/Ecuador (n=5)

max. pace*                                                          0.11-0.15

freq. drop of ending trill                                   100-500Hz

max. freq.                                                            4500-5000Hz

shortest note length                                          0.038-0.046s

*pace is expressed here as period, duration between two subsequent notes

 

devillei from the Amazon (except birds form C Bolivia) (n=6)

max. pace                                                            0.09-0.15

freq. drop of ending trill                                   0-900Hz

max. freq.                                                            4000-4900Hz

shortest note length                                          0.04-0.055s

 

devillei (from C Bolivia) (n=3)

max. pace                                                            0.045-0.05

freq. drop of ending trill                                   1400-1900Hz

max. freq.                                                            4400-5000Hz

shortest note length                                          0.016-0.024s

 

subochracea (n=5)

max. pace                                                            0.06-0.07s

freq. drop of ending trill                                   1100-1700Hz

max. freq.                                                            4000-4700Hz

shortest note length                                          0.02-0.028s

 

 

Birds of the isolated population in Colombia/Ecuador sing very much like devillei in the Amazon, with the song ending in a stuttering series of notes, at most slightly descending in pitch.

Birds of the race subochracea have a similar song, but notes end in a much faster trill which descends more in pitch. From the measurements shorter note length and larger frequency drop of the ending trill may lead to a score of resp. 2 and 2.

However, presumed devillei birds from C Bolivia (not N Bolivia) seem to have a song very much like subochracea, also with a trilled descending end (XC2533) (!). Unless this makes sense morphologically, a larger sample set would have to confirm this apparent anomaly.

Given that the vocal differences don't seem to match the present taxonomic treatment of subspecies, it seems safer not to score vocal differences until we have a larger set of recordings, especially from the SW Amazon region.

This note was finalized on 6th 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: Roger Ahlman, Nick Athanas, Peter Boesman, Tayler Brooks, Bradley Davis, David Geale, Niels Krabbe, Marcos A. Melo, Jeremy Minns, John V Moore, Jonas Nilsson, Sander Pieterse, 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: on57_striated_antbird.pdf