Congratulations on Boss. As I posted earlier, they are great dogs and were bred to be working dogs and to "herd" but it takes work on your part. Scarlett is now 10 months old and has finally learned to leave the ducks and peacocks alone and is now able to be left outside alone with them. Take Boss outside everytime you go out, to walk amongst the chickens - while you feed them and care for them. Hold them and let him sniff them while you pet it so he knows it's part of the family. As was just posted, a LGD must stay with his flock - Rex now stays outside at all times. Yesterday a stray lab wandered into front yard and Rex, who will greet an ax murderer with a ball in his mouth, had the lab down and pinned to the ground with his mouth around his throat. We were able to run the dog off. Had Rex not been outside, the lab could have gotten into the yard where all the chickens and peacocks run loose. He also chases every hawk he sees, barking and jumping and carrying on. Of course it's a big place to guard so that's why we got Scarlett. We also have another dog, a former stray, Lucy who stays outside unless it's really cold, and she too will chase off any predator whose scent she picks up. Even the former stray, Min Pin, Prissy takes off into the woods barking at things she smells/hears. She too has learned to sit/lay/walk amongst the flock without bothering them.
So, all that said, you can work with just about any kind of dog and teach it that the farm and all of it's animals are part of the family. We have 4 dogs and 2 cats, and they live happily and peacefully amongst a bunch of free roaming goats, peacocks, ducks, and chickens. I even have a "kitchen chicken" that is crippled and is just sitting in a spot on my kitchen floor and none of the dogs or cats bother it at all.
I think the ones that have the problem, and I know it's applied to me before, are the ones that try and keep the dogs tied up or separated and then when they get loose, they aren't familiar with chickens/ducks and either try to kill them or play with them. When we first got ducks, and kept them in separate pen, Lucy killed six in a minute flat without making a sound when she first got access to them - we fussed at her and introduced them to her and she hasn't bothered them since, not even the babies. Scarlett too killed four ducks when they flew out of their pen. Same thing - caught her in the act, fussed at her, introduced them to her and took her amongst them and she hasn't bothered them since. She was also catching and mauling my peacocks but after getting caught and being allowed to be amongst them all day, she ignores them too. In both dogs' cases, trying to keep the flock and the dogs separate resulted in dissaster but allowing them to all hang out together has been great.
BUT....it's my GSD, Rex who truly guards everything and when he lays down in guard position next to something, even I can't move him. He will actually growl at me to let me know he is guarding and will not be moved. He really loves a bin of baby chicks or ducks and will lay down to guard and nothing better come close to his babies. We have new baby goats that had to be brought into the house for the first few nights and Rex had to come into house and "guard" them and there was nothing I could do about it - he takes it that seriously.
Work with your GSD and you'll have a dog that meets the best of both worlds.