I don't think a heating pad will work for you bud, not with your temps.
I have quail to worry about this winter too and our temps are about the same.
I do get -28c(-20F) temps at night sometimes but it's mostly in the low -20's.
Two weeks ago, I swapped my normal waterers over for a heated horizontal nipple waterer. Quails can't play and poop in it now.
Took them about a day to learn to use them.
I'm using a ceramic heat emitter bulb for the heat source, 5 gallon bucket (not in the quail coop), a small water pump to circulate the heated water to and from the nipples.
The bucket is in an insulated box, the cpvc pipes are also insulated. And a cheap little device called an stc 1000 to read the water temp and turn the bulb on when needed.