I don’t really know how much bathing birds do in the winter; and frankly if the circumstances were the same how many times would you have chipped a hole in the ice and jumped in.
What is a necessity, regardless of the season, is drinking water.
Birds don’t eat a lot of snow; instinct tells them that’s a bad idea. One’s core temperature drops like ice cubes in a glass of water when something is consumed that is colder than one’s innards; and if one is not wearing enough “outers” hypothermia sets in. Yes, birds are wearing down jackets, and they are adequate for our climate, when water is available. But if they were supposed to eat snow they would have been endowed with a full length polar suit like their penguin cousin.
So they search; looking for that yard that has it all, seeds and libation.
Maybe you’ve got a bird bath out there already, still in use. I’m guessing you haven’t cleaned it in a while. Hey, if you’re bathing in it that’s one thing; but when it’s your sole source of drinking water you’d like its quality to be a tad better than the Ganges downstream. So give it good scrub; it will be the last time you’ll have to all winter.
One more important bit of info. Unless you are one of those that likes to see the birds come in for a landing only to find themselves slipping and skating over the ice, hitting the rim and toppling off into the snow. (that does sound kind of funny)
No! That isn’t funny(well, maybe a little funny)
No! it’s not.
(well I guess not)
You can buy a bird feeder heater. A little disc you plug in to keep the water from freezing. Key words “not freezing”. You won’t be creating a Turkish bath situation where the steam rises and obstructs your view of the party going on out in the ornithological hot tub. No it just keeps it from freezing.
This does raise an important thermal dynamic concern; if the water is not freezing it is evaporating. Please make sure you are filling it as needed. There’s nothing more frustrating than coming up to the pop machine parched, only to find all the pop’s gone. Birds have their ways of getting back at you. You don’t think it’s just a coincidence that there are a lot of birds hanging around the car wash stores do ya?