Green-winged Teal are a common winter resident.  They start showing up in September-November, and then are fairly consistently found in fairly small numbers through April.  Sightings drop off quickly during the first two week in May.  Three sightings from early August, 1995-08-03, 2005-08-10, and 2009-08-13 appear as outliers.

We see them most frequently at the ponds at Marymoor West (aka the Rowing Club), but they are also seen in the slough, the lake, and in seasonal puddle-ponds, or simply flying down the slough.