the Strait of Belle Isle is a major trans-Atlantic shipping lane with vessels from Europe transiting by Forteau nearly ever day (during the ice free season)
The IUCN account for Yellow-breasted Bunting (that lists this species as endangered)
http://www.iucnredlist.org/details/22720966/0
states: "the decline is likely to be driven by excessive trapping at migration and, in particular, wintering sites " and "thousands of males are also stuffed and sold as mascots, since their presence in the home is thought to confer happiness" and "At least locally, for example in Cambodia, birds are trapped for "merit release" in temples"
the bird's tail feathers are damaged in a way consistent with captivity and not often seen in wild birds
these^ points need to be considered in evaluating the Forteau bird's wild status
but other facts are also important...
Yellow-breasted Buntings are a long distance migrant with many records far outside their normal range
weather patterns during early- to mid-October in NL were extremely favourable for delivery of long-distance vagrants
Yellow-breasted Bunting vagrancy in the Western Palearctic (Britain) includes many records ranging from late August to late October with a peak in mid-September, records in Britain have fallen off the virtually none in the last decade, in correlation with the species breeding population collapse
I would say it is a toss-up - using the criterion of 'beyond reasonable doubt' we cannot reject the possibility that this individual is wild and got there on its own
countable