Acorns are one of the most important wildlife foods in areas where oaks grow. Creatures that make acorns an important part of their diet include birds, such as jays, pigeons, some ducks and several species of woodpeckers. Small mammals that feed on acorns include mice, squirrels and several other rodents. Such large mammals as pigs, bears, and deer also consume large amounts of acorns: they may constitute up to 25% of the diet of deer in the autumn. In some of the large oak forests in southwest Europe, traditionally called "dehesas", pigs are still turned loose in oak groves in the autumn, to fill and fatten themselves on acorns. 