Tomorrow is the Winter Solstice. Many people celebrate this in many ways. The unifying theme is that it is the shortest day of the year, and from that day forward, the days begin to become longer and longer. The celebrations are that of life (sun, warmth) over death (dark, cold).
I make my solstice celebration into a nod to one of the stories of the Christmas tree: that northern European pagans would go into the forest and tie presents of food to the branches for the protective spirits of the animals that the pagans depended upon for food and clothing. The protective spirits would be pleased and there would be plenty of game to hunt in the summer to come.
In short, extra food for the critters.
Thor sez: What? You said we could have extra!