Ducks, migratory and otherwise

Gonzalo Horna photographed this drake Mallard (which was accompanied by a camera-shy female) on the morning of December 6 on the Gatún river, about 2 km downriver from the Transisthmian highway. His boatman, who lives in the area, says that he sees these birds almost every year from october to the end of the dry season.
We think (at the risk of being called conservative skeptics) that these birds can't be safely called vagrant wild migrants. Wild Mallards winter south to central Mexico, even though some venture further south. Meanwhile, domestic Mallards are pretty common throughout Panama, and these birds were too close to houses and farms for comfort. Also, the chances of not just one but two adults overshooting their regular wintering location are pretty slight.
Also seen that day were Cocoi Heron, which is rare away from the eastern Pacific slope of central Panama, plus a Lesser Scaup in Gatún Lake.