I have seen birds fluff up their feathers in winter. I think it helps keep them warmer.Went to bed about 4-ish this morning - no snow. Got up around 11 - this is what greeted me! There is about a foot's worth on the round table (there really is an iron mesh table under there) and birds all over the feeders, ground, and trees. That puffball to the left of the male cardinal in the tree in the distance is a mourning dove. I've never seen one that fluffy!