Thats interesting Peepers! Yes dogs need guidance and training. In a pack working to protect sheep they would get this as youngsters from the rest of the pack and the shepherd of course. From what I've read and it makes sense chances of success are greater though with proven working stock but people seem to think all you need to do is throw them in with sheep, chickens or whatever as tiny pups, that they will imprint and all will be fine but this is far from the truth even if some do miraculously turn out OK.
Yes accidents are likely with big dogs and little fragile ones. My own dogs are not clumsy as such but when riled by something there is no question they dont stop to think where they're going to put their feet, a straight line is the quickest route and they will take it. Once and in a flash they've decided on the line of approach that's kind of it everything in their way is flattened. They seem to be part sight hound, part everything and very keen. They do notice birds of prey by the shadows they cast over the ground, and will chase those off if they ever try land nearby.
One of our distant neighbours had an elderly JRT taken by a Martial Eagle, they never saw it again. Once I was taking a short cut through some low hills in a conservation area with nephew when he was about four, we had his Teddy bear in the back window of the car and a Martial dropped out of the sky from no-where trying to get at that poor Teddy. All I saw was a flash of huge wing shoulders and face with crest feathers in disarray in the rear view-mirror, furious killer eyes pinned on Teddy, then it was gone. Back up into the heavens in seconds on a thermal column. So quick no dog could have stopped something like that. I often wonder at the speed of that thing, not a flap of the wing nothing, just straight back up from where it dropped. Those birds can spot prey from 5kilometers up in the sky. Magnificent birds they are too and don't cause much damage to livestock, not like hawks after chickens. They tend to prefer very desolate remote wild areas not agricultural or residential areas.
Think the Pyrenees is probably less reactionary or sharp as some of the more primitive LGB types, possibly softer more adaptable to things like chickens. I definately know mine would eat a chicken without hesitation, they've never seen one, but they took a gunea fowl with out a second thought, it flew into the fence in panic and they pounced. Cute maybe if I had trained them to chickens they could've been more mindful. Not entirely sure.