I'm sure you are correct on the hummingbirds - they are migratory here, so they must be the ruby-throated. The only birds we have that winter and are quite visible in the cold are the chickadees. I'm told that the squirrel feeder can double as a bird feeder in the winter months, and the chickadees will be thrilled to have a dry place to get seed. I've already seen them inside checking out the squirrel nuts and snatching little pieces, so it will be fun to get pics of them this winter doing just that!