I've had at least two hanging around my yard in Lake Forest Park this
summer. They have white backs and salt and pepper heads.

Here are a couple of pictures...

http://www.eskimo.com/~cekerns/birds/albums/uploads/bc_chickadee16.jpg

http://www.eskimo.com/~cekerns/birds/albums/uploads/bc_chickadee17.jpg

Craig Kerns
Lake Forest Park, WA
Backyard birding pictures at http://www.eskimo.com/~cekerns/birds