No, I'm not sewing teeny tiny outfits for them, but this fall I had a huge flock of hummingbirds that were constantly feeding at my feeders. When the extreme cold hit I was really challenged to keep their feeders from freezing. I hung a small heater under one of them, but then I noticed that the high winds were making it difficult for the birds to hang on to the wildly swinging feeders. So I decided to put the feeders on a small table near my patio door. They didn't seem to mind the new location but with the extreme cold they were freezing up very quickly.
Someone said they used handwarmers to keep the nectar from freezing as quickly. I remembered some of the sewing students making hand warmers for sale at craft fairs. They were basically Bean Bags filled with rice or wheat that are heated in the microwave. So I made small ones to attach to the glass bottle, and a large round one for the feeders to sit on.
When the larger round 'warmer pad' under the feeder was hot, it melted the snow and ice underneath and so the fabric became very wet. My solution for that was a thin sheet of plastic under the pad and on top of the snow. It worked quite well.