The bold white spectacles of the Cassin's Vireo are a good field mark. Blue-headed Vireo has brighter yellow flanks and more contrast between the head and back. Plumbeous Vireo is duller with little contrast between the head and the back and lacks yellow on the flanks. Black-capped Vireo also has white spectacles but it has a black, not gray, head. Yellow-throated and White-eyed Vireos have yellow spectacles. The Gray Vireo lacks spectacles and has faint wing bars.