Hummingbird feeder frozen up

I put up a hummingbird feeder six months ago and dutifully emptied, washed, and refilled it every few days ever since. But, although there were a few hummingbirds in town and even in my neighbourhood for weeks on end, I saw none at my feeder.

This morning when I got up, it had frozen overnight. So I have taken it down until next spring.

This is what it looked like before I brought it in.