Roast it if it looks sufficiently duck-like. Don't worry about whether it's officially a duck, just if it has the relevant features for roasting.
However, I don't understand the attachment to getting 3/4 of the way through the basting, stuffing and roasting project before suddenly discovering that you're trying to crisp a small piece of vaguely duck-shaped ornamental stonemasonry.
I agree with (often) only testing for the *relevant* features of duck-ness. But it seems like the best time to test for those relevant features is "as soon as possible", not "shut your eyes, and charge ahead until you fail". Is there a good reason for "fail fast, except for syntax errors, those we should wait to crash until we're actually trying to execute them"?
I've been working on my non-vegetarian metaphors, how did I do? :)
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