wingbars and spectacles; tinges of yellow (California, USA; 2007-04-22)
Cassin's Vireo Vireo cassinii
Native Range: North America
Notes:
very similar to Plumbeous Vireo bu slightly less grayish overall and with more olive tinges especially on back; part of the broader "blue-headed complex" of vireo species.
similar to Hutton's Vireo and Plumbeous Vireo (California, USA; 2007-04-15)
grayish head contrasts with spectacles (California, USA; 2007-04-27)