In the following we briefly analyze and compare voice of the different races of White-winged Black-tyrant (Knipolegus aterrimus). 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).
Male display flight is accompanied by a short phrase of a few notes. This phrase seems to vary among races, but although number of samples is small, there is clearly consistency within every population.
K. a. heterogyna (1 recording from Cajamarca): song of three notes: 1st note steeply downslurred, second slighly rising, third note overslurred and very buzzy in centre. Total length 0.56s, frequency 3100 - > 5100Hz (range 2000Hz).
K. a. anthracinus (3 recordings from Junin, Peru to W Bolivia): song of two notes: a very irregular trilled note followed by an overslurred note with a very buzzy centre (like end note of previous race). Total length 0.66-0.77s, freq. 3600 -> 5950Hz (range 2350Hz).
K. a. aterrimus IN PART (3 recordings from C Bolivia, S Bolivia and extreme N Argentina): song is a single note with a rising buzzy start and downslurred end. Total length 0.25-0.37s, freq. 4000 -> 5600Hz (range 1600Hz).
K. a. aterrimus IN PART (5 recordings from Argentina): song of two well-spaced notes: 1st note short and sharply rising, second note with a rising buzzy start and downslurred end (like note of previous race but shorter). Total length 0.6-0.62s, 1st note max. freq. 5600-6600Hz, 2nd note: 0.22s freq. 4100 -> 5300Hz (overall freq. range 1500-2400Hz).
K. a. franciscanus (0 recordings)
There is not a single race which clearly stands out vocally, they all are about equally different. Following Tobias criteria, we could give the following estimated scores:
heterogyna is the only one with a 3-note song and seemingly has the lowest max. frequency, and could thus be given a score of about 2 + 1 = 3 vs. all other races.
anthracinus has 2 long notes and the longest overall song length, with still fairly low frequencies, and thus could be given a total score of about 2-3 vs. all other races.
aterrimus NORTH is the only one with a single note song and a fairly narrow frequency range, and thus could be given a score of about 2 + 2 = 4 vs. above races and 2 + 1 = 3 vs. next race.
aterrimus SOUTH has the longest pause between the two shortest notes, and starts at higher frequencies.
Hopefully these differences can be confirmed when more recordings become available.
This note was finalized on 10th July 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, Steve Hampton, Dan Lane, Bernabe Lopez-Lanus, Niels Krabbe, Sjoerd Mayer, Mark Robbins, Andrew Spencer and Herman Van Oosten.
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: on146_white-winged_black-tyrant.pdf