Ones to look for: Cassin's Vireo

                                            

Separating Cassin's Vireo from Blue-headed Vireo can be impossible; some Cassin's are bright, and some Blue-headeds are dull. Looking for the less clear-cut border between the gray cheek and the white throat is the easiest clue to look for, but it can be ambiguous. Finding a Cassin's that doesn't approach Blue-headed in color and pattern is the best chance anyone has to prove a claim of a Cassin's in Blue-headed range. These photos of a pair of Cassin's near the nest were taken in Oregon in June 2022.

 

Out of order images from my trip to Oregon and back, early June 2022