ML619501435

Age

Not specified

Sex

Not specified

Observation details

A pale, rather drab solitary vireo seen briefly and photographed while it flew from branch to branch. Little contrast between greyish head and white throat, however, despite this bird's identification as a Cassin's Vireo, I believe this is just a dull Blue-headed Vireo. From others' photos, the shape of the rectrices indicates a definitive plumage bird, and what I can make out of the wing coverts supports an adult bird as well. Multiple photos showing the outer rectrix (r6) show a substantial amount of white for a Cassin's Vireo (which should have an indistinct to minimal white edge, as opposed to a distinct white edge), but which is well within range for Macaulay photos of Blue-headed (also compare Piranga tail spread for Definitive cycle BHVI). This bird has rather thin wingbars for a Cassin's Vireo, though it's possible the feathers are just worn. Cassin's may have brownish-grey feathers in the crown in its definitive plumage, which this bird does not. Overall, the dull plumage and some plumage characteristics absent may be due to the feather age, having last molted in the fall. The bird in my photo appears to have quite yellow (dull, but yellow) underparts, but Barry's photo at the same time is much paler. Underpart colour, especially from a relatively distant bird in a forest, is not a wholly reliable field mark in this case. The bird has exhibited breeding behaviour, remaining in the same general area all day, and been observed singing by others. In the same area, I observed a YTVI, which others reported was sitting on a nest. This bird was also reported to be sitting on the same nest prior to the YTVI. I recorded a singing vireo, a repeated burry "vireo." The repetition of the same phrase is unlike Cassin's Vireo, and the burriness is unlike Blue-headed though "Individuals known to sing faithful renditions of Yellow-throated Vireo song" (Birds of the World). The YTVI was not reported to be singing, though sitting on a nest in the vicinity. If my recordings are of this bird, as it was previously observed to be singing, then it is likely a male, albeit an incredibly drab male. This also brings the possibility that this is a BHVIxYTVI or a backcross of some sort, which has been discussed by others on eBird and on the Ontario Bird Alert Discord server.

Technical information

Model

Canon EOS R5

Lens

RF100-500mm F4.5-7.1 L IS USM

ISO

200

Focal length

500 mm

Flash

Flash did not fire

f-stop

f/7.1

Shutter speed

1/1000 sec

Dimensions

2664 pixels x 1782 pixels

Original file size

510.49 KB