In the following we briefly analyze and compare voice of the different races of Tawny-crowned Greenlet (Hylophilus ochraceiceps). 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 compared the following 3 groups:
North West (H. o. ochraceiceps, H. o. pallidipectus, H. o. pacificus, H. o. nelsoni, H. o. bulunensis): Song is a repeated drawn-out whistle, rather flat in pitch or slightly ascending.
(n=6) Average SD
min. freq. 2900 - 3500Hz 3275Hz 193Hz
max. freq. 3250 - 3850Hz 3658Hz 198Hz
total length 0.55 - 0.73s 0.64s 0.05s
freq. range 300 - 500Hz 383Hz 69Hz
# notes 1 1 0
Amazon (H. o. ferrugineifrons, H. o. viridior, H. o. lutescens, H. o. rubrifrons): Song is a repeated drawn-out whistle, rather flat in pitch, slightly ascending or descending.
(n=9) Average SD
min. freq. 2550 - 3200Hz 2707Hz 191Hz
max. freq. 3000 - 4100Hz 3202Hz 346Hz
total length 0.66 - 0.98s 0.76s 0.10s
freq. range 220 - 900Hz 495Hz 174Hz
# notes 1 1 0
Guianas (H. o. luteifrons): Song is a repeated phrase of two slightly descending whistles, the second one lower-pitched and longer than the first one.
(n= 8) Average SD
min. freq. 2750 - 3040Hz 2942Hz 87Hz
max. freq. 3600 - 4700Hz 4002Hz 343Hz
total length 1.10 - 1.56s 1.28s 0.16s
freq. range 560 - 1800Hz 1060Hz 350Hz
# notes 2 2 0
Surprisingly, the different song of luteifrons has seemingly nowhere been picked up in literature: its song consists of two notes with decreasing pitch (score 4), resulting in an overall longer song phrase (score 2-3) and larger frequency range (score 1-2). When applying Tobias criteria, this would lead to a total vocal score of about 5 vs. all other races.
Birds of North West and Amazon differ slightly, NW birds having on average a higher-pitched voice (score 1-2) and slightly shorter whistles (score 1). Total score 2-3.
The exact geographical boundaries between ferrugineifrons and luteifrons will need more study, to find out whether the two taxa co-exist or not. Interestingly, based on voice birds of E Venezuela are luteifrons (Guianan group) while birds of SE Venezuela are ferrugineifrons (Amazonian group), a pattern also seen in some other species. North of Manaus, most birds are luteifrons, but one recording is not (if correctly identified, it is a background voice on XC286603, and might equally be song of Collared Gnatwren Microbates collaris).
A single recording of presumed race lutescens (XC120183) apparently consists of a 2-note song, but else lacks resemblance with luteifrons. rubrifrons at the other hand sings 'normal' song. To be further investigated.
All in all, we can conclude that the Guianan group clearly stands apart vocally.
This note was finalized on 22nd October 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: on168_tawny-crowned_greenlet.pdf