I got beaked by a heron once.
And he wouldn’t let up either.
Kept poking me in the backside with his beak.
If you have an exterior weatherproof light fixture, a flood bulb of sufficient size, incandesant, should help keep it defrosted as long as the food is colored.
I don’t know how ot modify a feeder to accept a fishtank heater safely.
Don’t have a place to put a bulb close to where the feeder in back is. Altough I do occasionally see a hummingbird at one of the front feeders, it seems they’re predominantly using the one off the deck in back. If I can rotate that one with the other flat, plastic feeder and remember on nights when a really hard or extended freeze is expected to bring it in in the evening so it doesn’t freeze and crack, it should be okay.