Tweets,

My impression is that Fox Sparrows nest quite commonly at the edge of
boggy places in the Cascades of Washington on both sides of the crest,
generally above 4000 feet/1200 m. All that I've seen well, to the best
of my recollection, have been dark gray headed forms. There should be no
significant biogeographic break between this population and those in the
mountains about Vancouver.

Gene Hunn.