Bluebirds - Harbingers of Spring?

Bluebirds were flitting about the backyard this morning, following an overnight snow (note the snow on the branch lower right). Two downy woodpeckers were chasing the bluebirds from tree to tree, acting either friendly or territorial, not sure which, probably the latter. Although it was 15°F when this photo was taken, can spring be far off? I'd better get busy and clean out the bluebird houses around the property!