Thank you all for your suggestions! After reviewing the calls of all mentioned
birds, we found it - and it is indeed, as many of you surmised, a HUTTON'S
VIREO. We knew them to be in our area, but in 3-4 years of birding have never
seen them, nor knew it if we did hear them. How exciting to add this little
bird to our life list! We will be sure to keep plugging along in our bird ID -
I have found learning bird calls and songs to be the most challenging part of
this hobby for me, but well worth it. It is amazing how many different birds I
hear on my walks now that I never knew were there because I couldn't see them.
:)
Chris and April Lauman