The Plumbeous, Cassin's, and Blue-headed Vireos used to be considered a single species, Solitary Vireo. All three are very similar, with bright white 'spectacles', stout bills, and short tails. The Plumbeous, left, was photographed by Bill Schmoker in Colorado 5/02, the Cassin's by David Elwonger fall 2003 in Colorado, and the Blue-headed, right, was photographed by Jay Gilliam in Iowa 10/03 The Blue-headed is brighter and more contrasty with strong contrast between the auriculars and throat. The Cassin's has intermediate plumage between Blue-headed and Plumbeous.