Hello! Your photo is very intriguing and provided me with almost 20 minutes of thinking. Both Plumbeous and Cassin's share a lot of field marks, so my conclusion is the result of studying the differences. I believe your bird is a Plumbeous Vireo, and here's why: 1) although the photo only shows a little bit of it, the edges on the secondaries are gray. Cassin's would be greenish, or at least tinted in some color other than gray. 2) the tail is pretty short, and I realize that this is a relative measurement, but after considering both the camera angle and bird's posture, the tail's length leaned toward Plumbeous to me. 3) it's important to note that Plumbeous can have faint yellow wash on the flanks. However, after reviewing the photography aspects (lighting, surroundings, etc.) I concluded that the yellowish coloration on the undersides of the bird are the result of the bright sun reflecting off the nearby, young leaves. That would also explain how the yellowish tint on the photo seems to be almost uniformly spread out on the entire underside of the bird. It should be known that I'm no expert on Vireos, and am still enjoying learning this fun family of birds too, so take this with a grain of salt!
The birds are happy, and so am I ~Caleb Alons, Larimer County -- You received this message because you are subscribed to the Google Groups "Colorado Birds" group. To unsubscribe from this group and stop receiving emails from it, send an email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/0fa45ce0-a549-4db5-b8f1-8b4152275a65%40googlegroups.com.
