In the following we briefly analyze and compare voice of the different races of Northern Rough-winged Swallow (Stelgidopteryx serripennis). 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).
We have only found two recordings of races ridgwayi/stuarti (ML139404 and ML139412, recorded by Greg Budney in Tikal, Guatemala on 18-26 March 2009. We assume these are indeed stuarti, based on distribution and slightly different voice, but we can't be entirely certain as northern races may also reach this region during winter): Song or excited calls?, flight call and song or excited calls?, and flight call (illustrated by sonograms in the pdf version of this note).
Examples of other races: Song or excited calls?, and flight call.
Flight calls of ridgwayi/stuarti seem to be very similar to other races, but possibly slightly lower-pitched. Excited calls or song are somewhat different, with notes seemingly covering a wider frequency range (bandwidth 4-6kHz vs c. 3kHz). If confirmed by more recordings, this would lead to a vocal score of about 2.
This note was finalized on 17th February 2016, 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: on239_northern_rough-winged_swallow.pdf