To be honest, I HATE killing things. even those nasty house sparrows; there's nothing good about them, nothing. still, taking a life is pretty huge karmically. when i was a kid and didn't know any better, i lived on a farm in texas. i shot everything that moved. possums, jackrabbits, cottontails, owls, coons, skunks, armadillos, squirrels (ate them). In any case, to this day it grieves me to think about it because it was so unnecessary and i know i caused suffering needlessly.
in the case of these Herons, they are trespassing. And they are predators. And they are attacking our pets. So, it'll be a very, very sad thing for me if I ever have to kill one, but I will. Right now it looks like the Scarecrow will do the trick. And, before I kill a Heron I'll buy that other newer deterrent with the noise, light and mirror. Might even consider fencing our dogs by the pond when we're not home. I'd really very much rather not shoot one notwithstanding the fines and penalties.