Just looked it up on Amazon, it's meant for bird baths, and doesn't say how much water it can heat. My waterers are way bigger than bird baths!
Still seems that it's defective, totally agree about having GFI outlets, but it wasn't used for it's designed purpose.
Mary
Water and electricity are a scary mix; I only use heaters as they are meant to be used, and aquarium heaters don't belong out there in below room temperature situations.
So glad you figured out that this heater was a bad thing, before your birds were injured, or seriously dehydrated because...