It seems pretty clear that the game is that you ONLY do the feeding in winter and don't also do the first 6 phases of the regular turn, however it's not 100% clear that you don't. The rules mention that the first three seasons are "normal" and that indicates that this is like a shogun where the winter turn is only about feeding. However, they list the feeding portion of the winter as a seventh phase on both the player board and the rules- that would indicate that you play a full turn in the winter and add in the 7th phase at the end of that full turn.
We played that the winter is ONLY feeding and no actions.
Also...does the start player marker pass at the end of winter as well if so? In a 3 p game, the same player will start each year if not.