Gadwall can be seen at Marymoor year round, and have been noted with young about every other year.  They are not nearly as common as Mallards, but they are often seen with them.

Gadwall numbers and frequency of occurrence have declined notably in recent years, from an average of 44 sightings a year from 1995-2005 to an average of 30 sightings a year since then.  This occurrence pattern is very close to that of American Coot, which has also seen (even greater) declines.  One might speculate that both species have declined due to a decrease in food availability and/or an increase in predation by Bald Eagles.  However, Gadwall are well known to kleptoparasitize American Coots - that is, they swim with a flock of feeding coots, which can dive deeper than Gadwall.  When a coot returns to the surface, the Gadwall will snatch some of the vegetation brought up by the coot.  We used to witness this frequently among the large coot flocks on the lake.  Gadwall numbers may be down due to the decrease in coot flocks on which the Gadwall were relying on for food.

Gadwall are most often found in the slough, with large American Coot flocks on the lake, or on seasonal puddle-ponds anywhere in the park.  They will also forage on mowed sports fields.