The turkey was brought to Europe in the early to mid 16th Century, and spread rapidly (possibly as a novelty) amongst the nobility under names such as 'indian chicken'. Prior to the 16th Century, turkey was definately not available in Europe, and should be considered a non-period food for any feasts themed earlier than the 16th Century. Serving gamebirds that are seldom served today, but well known to medieval palates (eg. grouse, peacock, swan (if you can get it)) at feasts, may better replicate the atmosphere of a 16th Century nobleman being served turkey at a feast. There is little evidence of turkey spreading to the lower classes during the 16th Century.