Hi Steve and Keith,

I don't know if this will help or not, but how was the bird behaving? I
have had several experiences with Bell's Vireo both in the West and East
Coast.

As consistent with Sibley's guide, I have seen several Eastern birds bob or
pump their tails like Palm warblers while on one or two occasions seen
Western birds act like a gnatcatcher by wagging their tails up and down and
sideways as well.

Bell's are rather active in their movement and to me, behave almost wren or
tit like but much more secretive. As a consequence, a challenging bird to
photograph :(

Also, their long tail gives them quite an elongated look compared to other
vireos.

Good birding,

Khanh Tran (Portland, Oregon)