Allan, 

Re the barnacle goose: my personal philosophy about potential escapes is
that, unless a bird is wildly unlikely to be a genuine vagrant, then it
should only be considered of uncertain origin IF it actually bears some
signs of captivity (feather wear, leg bands, unusual behavior, etc.). If
it is not wildly unlikely, its remiges and retrices are not badly worn,
it has been keeping company with other birds that may denote its
origins, and its behavior is "natural", then the "default" attitude
should be that it is most likely to be wild. 

The barnie satisfies the last four criteria: no signs of feather wear or
leg bands, associating with a huge flock of canadas (many of them
lessers), greater white-fronts, snows, and a cackling goose or two. Also
the barnie, like the rest of the geese in the flock is highly nervous
about humans - very difficult to get closer than a few hundred yards.
This is one where I would say that a captive origin is unlikely.

FYI, Dick Veit wrote an interesting article for Bird Observer recently
about the whole issue of how we should regard potential "escapes". I
think that he makes a good deal of sense. 

Hector Galbraith PhD
Galbraith Environmental Sciences LLC
837 Camp Arden Rd., Dummerston, VT05301
802 258 4836 (phone)