A black-capped chickadee. Despite their small size, the chickadees stay around all winter no matter how cold it gets and add some life to the otherwise rather bleak environment.
They travel in flocks, especially in winter, and stash food in many different hiding places. Their memory is exceptional and allows them to retrieve the hidden food as they need it. In autumn, the part of their brain responsible for spatial memory (hippocampus) grows in size to retain the knowledge of where the food is stored, and shrinks again in the spring when they no longer need to retain the information.