I'm surprised that some of the more vocal members on tweeters didn't catch
this, but JUVENILE Zonotrichias are heavily streaked below, and
without head stripes. This plumage is only worn a short time after
fledging, after which they molt into first-winter (or more accurately
first basic) plumage. Due to the time of year, I'm assuming that the
hybrid that Jon Anderson banded was a first basic bird.

Anyway, in looking through the Zonotrichias in the collectin at the
Burke Museum, first basic white-crowned sparrows DO NOT have a distinct
white throat bordered by black malar stripes; Jon your bird does sound
like a white-crowned x white-throated sparrow. Cool!

There's a neat article in the July 1979 issue of the Auk, describing a
hybrid white-crowned x Harris' sparrow, and a white-throated x
golden-crowned sparrow.

Mike Donahue
Seattle