Mike North, a wildlife biologist at the Minnesota DNR, discusses the role of woodpeckers in the ecosystem and how foresters and landowners can keep these populations healthy. Have you ever been out on a cold winter day, spotted a woodpecker hole in a tree, and wondered what kind of critters might be cozied up in there? I sure have. The Minnesota DNR is investigating tree cavities of various sizes, and their findings re-emphasize the importance of woodpeckers to the forest ecosystem.