Speculation from the Stokes' blog entry last year:
So many questions remain. Are the 2005 and all the 2006 sightings all of the same bird? Where did the bird come from in the first place? How long will it stay this year? Where will it go next? Is there some special wintering place it goes to in this hemisphere, that no one has yet discovered? Hmmm, maybe we should all be checking out the herons in Florida this winter, maybe its hanging out with the Snowys and Tri-colored Herons there. Or maybe it winters in Barbados or elsewhere in the Carribean.
And, of course, one of the biggest questions is, is it a Western Reef-Heron in the first place, or maybe a dark morph Little Egret, as current research suggests. There are some fascinating behavioral observations on the Western Reef-Heron seen in Newfoundland in 2005. That bird was seen in the company of a Little Egret (another rarity there at the same time.) The two birds were seen frequently feeding together and often the bird identified as the Western Reef-Heron would pick up twigs or sticks and present them to the Little Egret!
http://stokesbirdingblog.blogspot.com/2006/09/western-reef-heron-continues.html