A First Record of Yellow-green Vireo (Vireo flavoviridis) for British Columbia and Canada. By Rick Toochin and Gary Thoburn. Revised: June 10, 2023.

The Yellow-green Vireo (Vireo flavoviridis) is a small passerine that breeds from southern Texas (occasionally in the Rio Grande Valley) in the United States, and the western and eastern mountain ranges of northern Mexico (the Sierra Madre Occidental and Sierra Madre Oriental), south through Central America to central Panama (Howell and Webb 2010). Yellow-green Vireos are migratory birds that winter in the northern and eastern Andes and the western Amazon basin (Howell and Webb 2010, Hoyo et al. 2010). The species is casual or accidental along the Baja Peninsula of Mexico (Howell and Webb 2010). In North America, outside of southern Texas, Yellow-green Vireos are accidental in Nevada, Arizona, Louisiana, Alabama and Florida with extralimital records coming from Bermuda, Barbados and Venezuela (Hamilton et al. 2007, Hoyo et al. 2010). It is a regularly occurring species in California in the fall (Hamilton et al. 2007). In Canada there is a specimen record for Godbout Quebec taken on May 13, 1883 (Godfrey 1986). This specimen is now contested by some authorities because it is faded and damaged (Phillips 1991). Recently further examination of the bird revealed that it may actually be a Red-eyed x Philadelphia Vireo (Vireo olivaceus x Vireo philadelphicus) hybrid (Phillips 1991); but others have measured the specimen and found the measurements fall within the correct lower range to Yellow-green Vireo (Holder 1996). It is suggested that only DNA analysis will rectify the controversy (Hamilton et al. 2007). With that in mind, a recent photographic record from Vancouver, British Columbia, is likely the first record for not only the Province, but possibly for Canada.

 

The identification of Yellow-green Vireo is covered in all standard field guides to North American birds. Yellow-green Vireos are very similar looking to Red-eyed Vireos, but with some key differences. The Yellow-green Vireo is a little larger in body size to the Red-eyed Vireo, and this also makes it a little heavier in body weight (Sibley 2003). The Yellow-green Vireo has a drab light gray head pattern with a light inconspicuous eye line that runs through the red eyes, no dark line from the base of the bill through the eye and a heavy long pale bill (Sibley 2003, Dunn and Alderfer 2011). An important feature of the Yellow-green Vireo is that the sides of the neck have a bright yellow wash which extends down onto the flanks and ventral area (Sibley 2003, Dunn and Alderfer 2011). The amount of yellow on the sides of the breast can vary, but the yellow along the side of the neck is found on both bright and drab individuals (Sibley 2003, Dunn and Alderfer 2011). The central breast area is white in colour and varies on the amount of white, given that some birds are extensively yellow in colour (Hoyo et al. 2010). The wings and back of the Yellow-green Vireo are a lighter, brighter yellow-greenish colour that extends down the back and onto the tail (Sibley 2003, Dunn and Alderfer 2011). The tail is also a light yellow-greenish colour, and is square shaped and often held in an upright position (Sibley 2003, Dunn and Alderfer 2011). The legs are gray in colour (Sibley 2003). The song of the Yellow-green Vireo is similar to Red-eyed Vireo, but is shorter and less musical with shorter pauses between phrases, and is reminiscent of a House Sparrow (Sibley 2003, Dunn and Alderfer 2011). Call notes are similar to Red-eyed Vireo (Sibley 2003).

 

Red-eyed Vireos are slightly smaller in body length and weight to Yellow-green Vireos (Sibley 2003, Dunn and Alderfer 2011). The Red-eyed-Vireo has a dark gray cap that has a black lateral crown stripe that runs from the bill base to well behind the red eye (Dunn and Alderfer 2011). Below this is a distinct pale eye stripe going from the bill base to behind the red eyes (Sibley 2003, Dunn and Alderfer 2011). An important field mark is the dark line that runs from the base of the bill through the eye towards the nape (Sibley 2003, Dunn and Alderfer 2011). This marking is not found on Yellow-green Vireo (Sibley 2003, Dunn and Alderfer 2011). The bill of the Red-eyed Vireo is large and long for a North American Vireo, but is not as thick or long as the Yellow-Green Vireo (Sibley 2003, Dunn and Alderfer 2011). The cheek has a dark wash of olive colour with the throat being white and the sides and breast also being white (Sibley 2003, Dunn and Alderfer 2011). There is a light wash of yellow on the vent that can vary from drab birds to bright birds, but it is never extensive or as bright as on a Yellow-green Vireo (Sibley 2003, Dunn and Alderfer 2011). The back, wings and tail are bright olive colour that are dark and lack the yellow tones of Yellow-green Vireo (Sibley 2003, Dunn and Alderfer 2011). The legs are gray and the tail is often held in an upright position (Sibley 2003, Dunn and Alderfer 2011). The song of the Red-eyed Vireo is loud simple series of hurried phrases with definite pauses in between the phrases that sound like “her-I-am, in –the-tree, look-up-at-the-top” (Sibley 2003). The call note is a loud nasal mewing “merrf” sound (Sibley 2003). Given that these two species are closely related, any overly yellow necked and breasted “Red-eyed Vireo” reported in the fall anywhere in the Province should be scrutinized carefully, especially looking at the facial features to make sure the bird is not a Yellow-green Vireo.

 

The Yellow-green Vireo is a species that regularly wanders into California in the fall from Mexico with there being eighty-two accepted by the California Bird Committee as of 2007, and is reported annually each fall (Hamilton et al. 2007). Though not recorded in Oregon or Washington, given the frequency of records for California, it seems only a matter of time before this species will be found in these two states (OFO 2012, Wahl et al. 2005, WBRC 2012). British Columbia’s and probably Canada’s first record was found in Stanley Park, in Vancouver on September 18, 2013, by one of the authors who was travelling through the area from Great Britain. The bird exhibited classic vireo behaviour by staying low in the foliage and not coming out for better views. It was watched for ten minutes and photographed before disappearing deep into the foliage. Due to the similarity to Red-eyed Vireo, and the unlikelihood of the bird being a Yellow-green Vireo, one of the two observers in the group didn’t look at the bird, believing it had to be a Red-eyed Vireo based on the range of that species. As a result the bird was at first thought to be the similar looking Red-eyed Vireo, but upon further review, the photographs proved this bird to be a Yellow-green Vireo (J. Fenneman Pers. Comm.). The timing of this record fits perfectly into California’s pattern of fall vagrancy, where Yellow-green Vireos appear in small numbers between second week of September till the third week of October (Hamilton et al. 2007). Given Red-eyed Vireo is an early migrant in the fall with birds moving in August through early September (Campbell et al. 1997), any odd looking Red-eyed Vireo seen after September 15th should be scrutinized by observers for a potential Yellow-green Vireo (Hamilton et al. 2007). This species could easily turn up in the Province again and is possible anywhere. Now that all British Columbian observers are aware of this bird, it very likely will turn up again in the future in a migrant trap or banding station somewhere in the Province.

We wish to thank Paul Levesque and Barbara McKee for reviewing the manuscript. A special thanks to Jamie Fenneman on further information about the identification of the Yellow-green Vireo. We also wish to thank Andy Birch and Russell Cannings for getting the word out to the birding community, and bringing this record to everyone’s attention. All photos are used with permission of the photographer and are fully protected by copyright law.

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