I will add that Russ's map shows what units they are in, not necessarily that they are spread throughout those units.
They are few and far between on the Wetside. Never have heard of seen one in Snohomish County in 21 year s. There is a very limited area in Thurston County were they can be found regularly, and very few and far between on the outskirts of that. I would say hardly any, if any in Winston or Ryderwood Units as well.