Joey:
Given a view of the back, Blackburnian is actually fairly easy to differentiate from similar-looking species by the white or whitish "braces" -- those streaks of contrasting pale near the sides of the back. However, your major concern with identifying Townsend's Warbler (TOWA; note the lack of an "h") is differentiating from Black-throated Green Warbler (BTNW). One of the obvious differences between TOWA and BTNW is the latter's yellow-green vent strap (a complete or not-so-complete band extending from flank through vent to flank), so nicely illustrated in your first picture. An additional concern with these two species is that they are known to hybridize, and Colorado has at least two records of such. I am a little concerned by the apparent darkness of the rear corner of your bird's auricular patch (which might suggest TOWA genes), but that could be a posture or photographic effect.
For the Empidonax, I would guess that the bird's long primary projection and relatively shortish tail suggest Hammond's, a very different look than that of Dusky (short primary projection, long tail) and a somewhat different look than that of Least (short primary projection, shortish tail).
The vireo is, indeed, a Cassin's, as suggested by the overall greenish coloration and the dull interface of throat and auriculars; Blue-headed would have a bright white throat sharply and strongly contrasting with the auriculars.
Enjoy,
Tony Leukering
currently Cut Bank, MT
Given a view of the back, Blackburnian is actually fairly easy to differentiate from similar-looking species by the white or whitish "braces" -- those streaks of contrasting pale near the sides of the back. However, your major concern with identifying Townsend's Warbler (TOWA; note the lack of an "h") is differentiating from Black-throated Green Warbler (BTNW). One of the obvious differences between TOWA and BTNW is the latter's yellow-green vent strap (a complete or not-so-complete band extending from flank through vent to flank), so nicely illustrated in your first picture. An additional concern with these two species is that they are known to hybridize, and Colorado has at least two records of such. I am a little concerned by the apparent darkness of the rear corner of your bird's auricular patch (which might suggest TOWA genes), but that could be a posture or photographic effect.
For the Empidonax, I would guess that the bird's long primary projection and relatively shortish tail suggest Hammond's, a very different look than that of Dusky (short primary projection, long tail) and a somewhat different look than that of Least (short primary projection, shortish tail).
The vireo is, indeed, a Cassin's, as suggested by the overall greenish coloration and the dull interface of throat and auriculars; Blue-headed would have a bright white throat sharply and strongly contrasting with the auriculars.
Enjoy,
Tony Leukering
currently Cut Bank, MT
Need ID Help from Crow Valley (Weld County)
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