John, I also have limited experience on these guys but compare your photos to a bird I photographed two days ago near Lyons that I felt was a Cassin's (instead of Blue-headed) based on the lack of contrast between the head color and back color and the less than crisp contrast between the cheek color and the white throat (a mark that Sibley emphasizes in his second edition.)
<https://lh3.googleusercontent.com/-CzmzvarddVs/WbMVFZOOe3I/AAAAAAAAQ4E/b6eCXDgE3QY5kfZUeaye5FAEHK7en8oPACLcBGAs/s1600/P1020383_cr.jpg> Carl Bendorf Longmont Colorado Birding Adventures <http://coloradobirdingadventures.com/> On Friday, September 8, 2017 at 6:12:46 AM UTC-6, John Oliver wrote: > > Birders, > > This afternoon, between 4 and 5 PM while I was exploring the > Matthews-Reeser Bird Sanctuary by Lake Estes in Estes Park, I encountered > among the decent migrant flocks a Cassin's/Blue-headed-type vireo of whose > identity I'm not quite sure. Cassin's is of course more likely on > probability, and on top of that I have very limited experience with > Blue-headed, but nevertheless, this bird was noticeably quite brightly > colored and seemed to have a very contrasting facial pattern. I'd > appreciate the opinions of others on this particular bird. Luckily, I > managed to photograph the bird before it disappeared, and I've attached a > few pictures to this message for the review of others. Here's a link to the > eBird report as well, with an additional photo: > http://ebird.org/ebird/view/checklist/S39058674. I have a few additional > photos (not as good as the ones linked to here) if anyone else wishes to > see them. > > Thanks, and good birding, > John Oliver > Estes Park, CO/La Crescenta, CA > > > -- 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 post to this group, send email to [email protected]. To view this discussion on the web visit https://groups.google.com/d/msgid/cobirds/e366eabc-c05f-4103-8fdd-26f8ff4f0131%40googlegroups.com. For more options, visit https://groups.google.com/d/optout.
