This is my best guess as to which Vireo it might be - Cassin's Vireo. A quote from All About Birds on this species was enlightening. "This species is readily attracted to pishing sounds." So I now know the whispering noises I make to attract birds is called "pishing". Which is how the sound is spelled and uttered as "pish, pish, pish, pish" varying the pitch, volume and length until the right combination brings the birds in.

This one only gave me a precursory once over glance and kept going. I got two shots. This one and a front profile shot. Then off he went.

Canon T7 with Canon 70-200mm zoom lens @200mm, handheld.

Cropped, sharpened.