I have several Tibetan Mastiffs that are GREAT poultry guardians, one of my best males (finished AKC champion as well) watches the skies for predators and though the breed is NOT a herding breed, he walks towards the free ranging birds and they sort of group and walk back towards the coop. Then he goes for the other half the birds that didn't go in. He is absolutely the best! A half sister of his (same sire, different dam) is a bona fide fox killer, she doesn't ravage the fox, just one massive bite over the shoulders, puncturing the lungs, maybe the heart and she leaves it.
Some of my younger girls have very high prey drive and are NOT good around the birds! Horses, goats, cattle, no problem but the birds are too tempting to them so if you choose a LGD, make sure your breeder has done some temperament testing as to its reactions to birds, i.e., low or high prey drive etc.,