[Tweeters] Wylie Slough - Bird ID Help Needed

[Jim Betz via Tweeters]

Hi,
   I was at Wylie Slough today (yes, the eagle chick is -still- on the nest)
and saw a medium-sized bird (slightly larger than a robin) that had a
long body, dark/black on top and white belly.  Medium length bill. And
medium length dark tail.  The bird was sitting on a branch about 20 feet
from me - it flew away before I could get the camera up.
   It was not a shorebird of any kind.  The coloring was 'solid' not 
mottled.

   I am thinking "jay" or "mockingbird" ... but searches for either - in
ebird - did not produce any strong hits for Skagit County (especially at
this time of year and at Wylie or similar habitat).

   anybody?
                                     - Jim in Skagit