My daughter just asked me when she grows up, if she could marry a stick bug... then goes... well, I guess I really wouldn't want to marry one, they can't do the dishes.
This, I agree with. My dogs stay on my property, or near enough it to not bug my neighbors. (we have a small dog that gets out, but she just goes across the street to see the horses and comes back.)
She came with our house, and as such, she was already "trained" when we got her to see the...
Of course, not all dogs can be trained... but some breeds of dogs, are more likely to be trainable to leave cages alone, and protect the flock/yard from other predators.
They have a lot of videos on youtube on how to train your sheep dog to watch and alert to hawks and air-predators like owls...
Have you considered getting a dog that can be trained to protect your flock, yard and property? That might be enough to deter unwanted dogs.
Sheep dogs, Great Pyr's, and some others, can be trained to protect your birds. it might be cheaper than thousands in fencing.