Here in Canada the haggis season starts November 30th when the first kill of the season is celebrated on St. Andrew's day. The celebration at the end of the season is Robbie Burns day. Christmas, which starts on Labour Day Weekend (the first weekend in September) of course overlaps this which is why so many of the decorations and clothes are a festive plaid. Your haggis hounds may have seen their first Christmas decorations appearing in a store and this may be what set them off. It is an understandable confusion.