Proposal (849) to South American Classification Committee



Add Vireo gilvus (Warbling Vireo) to main list


A single Vireo gilvus was photographed at Jardín Botánico de Quito, Ecuador, by Roger Ahlman (Freile et al. 2019; on 11 April 2017. This bird was first heard calling, later observed and photographed. It responded to playback of nominate subspecies and approached, letting Ahlman to secure a few photographs. This observation was carefully studied by the Comite Ecuatoriano de Registros Ornitologicos (CERO), and it received unanimous votes for acceptance. The dull tone of upperparts, dull buff on underparts, poorly outlined, fairly broad whitish supercilium (and calls) were good characters for V. gilvus.


This is the first documented record for Ecuador and South America.



Freile, J. F., A. Solano-Ugalde, D. M. Brinkuizen, P. J. Greenfield, M. Lysinger, J. Nilsson, L. Navarrete & R. S. Ridgely. 2019. Fourth report of the Committee for Ecuadorian Records in Ornithology (CERO) and a revision of undocumented and erroneous records in the literature. Revista Ecuatoriana de Ornitología 5: 52–79.



Juan Freile, March 2020




Comments from Robbins: “NO. This appears to be based solely on photographs and a very poor (I'm not certain I can detect a vireo) audio recording attached to an eBird checklist.

“1) From the photos in the publication one cannot distinguish a worn Brown-capped (Vireo leucophrys) from a worn Warbling Vireo -- based on my examination of skins in the KU collection.  Note that this was in April.


“2) The audio recording offers nothing in support of the identification.  Vireos are notorious in responding to non-specific vocalizations (pers. obs.).


“3) The only way that I would accept a record of gilvus in South America is to either have genetic data or have a bird with one or more of the following data: banded/geolocater/transmitter.”


Comments solicited by Remsen from Dan Lane: “I disagree with Mark that this bird cannot be identified to Warbling Vireo with confidence, and feel he is being a far too conservative with his criteria for accepting a record of the species in South America. Comparing the photos of the bird in question:


Warbling Vireo - eBird


Warbling Vireo - eBird

Drab gray bird lacks any distinctive features. Eyebrow is slightly paler than rest of head and underparts lack p...


“With photos of Vireo leucophrys from Ecuador:®ionCode=EC


Brown-capped Vireo - Media Search - eBird and Macaulay Library

Search millions of photos, audio recordings, and videos of wildlife; powered by Macaulay Library and eBird. The ...


two things jump out immediately.


“1) the species name of V. leucophrys wasn't an accident! The glowing white supercilium contrasts strongly with the eyeline and crown in *every* photo in this series. Furthermore, the crown has a distinctly dark brown (again, a character highlighted in the English name of the species) lower edge where it meets the supercilium, exaggerating the pale eyebrow effect, and almost suggesting the black line present there on V. olivaceus. These characters are missing from the bird in question from Quito.


“2) in the photos of V. leucophrys, there is a strong hint of the warm yellow wash to the underparts contrasting with the whiter throat, even in the most faded or least-saturated. This does not appear in the photos from Quito, where the underparts are fairly uniform buff, with no suggestion of yellow.


“The states of both of these characters in the photos from Quito are consistent with Warbling Vireo, and not with Brown-capped. 


“I would agree that the response to playback and the recording made are not strong characters for conclusive ID to Warbling Vireo, but I can at least say that the vocalizations in the recording are of a member of the V. gilvus/leucophrys complex, and are calls given by V. gilvus.


XC182706 Warbling Vireo (Vireo gilvus)


XC182706 Warbling Vireo (Vireo gilvus)

Two agitated individuals. Habitat: bushes, mature deciduous forest, river. bird-seen:yes playback-used:no

XC105673 Warbling Vireo (Vireo gilvus)


XC105673 Warbling Vireo (Vireo gilvus)

natural calls from one of a pair. Both members of the pair were moving low through skunkbrush and junipers on t...


“Personally, I feel absolutely confident that this record is correctly identified as Warbling Vireo, and would be willing to accept it as the first record for South America. Whether it represents a member of the eastern nominate subspecies or western swainsoni-group may not be determinable from the evidence, although obviously likelihood would favor nominate.


Comments from Jaramillo: “YES.  I was going to say no, based on the fact that the looking at the photos in the publication, the color tones are just off to me.  A darker cap above the supercilium is not unusual in Warbling Vireo, but the tones there are usually gray toned, olive with a gray wash.  This bird, at least in the photo, looks mid brown. But then I saw that the eBird checklist has additional photos, and particularly the one where it is sallying to get a bug, is 100% Warbling Vireo. Here are the additional photos:


Comments from Claramunt: “NO. I think the evidence is insufficient.”


Comments from Areta: “YES. After carefully studying the photographs and refreshing my experience with V. leucophrys, I think that the bird in the pictures is V. gilvus. I can hardly listen to what is being made by the bird in the recordings, so I cannot comment much on this front.”


Comments from Pacheco: “YES. Based on the comments and examination of the additional evidence I accept that there are reasons to agree to the identification.”


Comments from Bonaccorso: “YES. I think Dan Lane's examination is adequate and justifies the inclusion of Warbling Vireo in the list. Mark, I think we cannot be as conservative as we used to be. These cases will surely increase in frequency as climate patterns keep changing.”


Comments from Dan Lane (who has Stiles’s vote on this one): “Yes to accepting to vote in Gary's place in this instance, and YES to accepting Vireo gilvus onto the SACC list for South America.”


Additional comments from Robbins: “I looked at the additional photos that are in the eBird checklist and I’m not convinced any of the photos demonstrate that the bird has a gray crown vs. a brown crown.  As I mentioned before, at this time of year, both species should not be in fresh plumage.  We have specimens of leucophrys in our collection (but not from Colombia or Ecuador) that are worn and have very little yellow on the flanks; they appear very similar to worn gilvus. 


“So, in my opinion, what is needed is a comparison of birds from the pertinent time of year and location.  As a result of Dan’s comments, on May 8th, I emailed Nate Rice at ANSP, where there are pertinent specimens, i.e., specimens of leucophrys from Colombia/Ecuador during the appropriate period.  Unfortunately, Nate still does not have access to the specimens.  I presume that is also the case for other museum colleagues.  Thus, I plan to stay with my original assessment until others can examine specimen material and offer their assessments.”