In the following we briefly analyze and compare voice of the two races of Slaty-capped Flycatcher (Leptopogon superciliaris). 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 of L.s.superciliaris is quite similar over its entire range. Despite a fairly extensive vocabulary, the vocalization heard mostly by far is a nasal double note "whit!-cha", sometimes in a short series and preceded by a few short introductory notes. This is presumably the day-time song
Voice of L.s. albidiventris seems to be more varied, and a similar double note as superciliaris is often heard as part of a more extensive phrase.
I will compare here this double note solely, although it is not entirely clear if this vocalization has the same function in both races:
L.s.superciliaris(n=8): Despite quite some variability, the second note is normally short and always downslurred
length 1st note 0.05-0.075s
length 2nd note 0.04-0.19s
max. freq. 1st note 1850-2590Hz
max. freq. 2nd note 1900-2500Hz
total length 0.21-0.36s
freq. range 1000-1500Hz
L.s. albidiventris(n=7): Despite quite some variability, the second note is always rather long and ends upslurred (the second note is actually often distinctly bisyllabic) "whit-t-cheee".
length 1st note 0.05-0.14s
length 2nd note 0.20-0.36s
max. freq. 1st note 1600-3400Hz
max. freq. 2nd note 1750-2800Hz
total length 0.38-0.60s
freq. range 750-1800Hz
albidiventris differs in having a longer double note (score 2-3), with a longer second note (score 2-3) which is upslurred instead of downslurred (score 1-2). Both races can thus be easily identified. If we apply Tobias criteria on this vocalization, total score for vocal difference would be about 4-5.
This note was finalized on 1st July 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: on119_slaty-capped_flycatcher.pdf