I agree with ohhhdear's assessment of some of the breeds. A dog with a high prey drive will never be safe with a flock. The breed will tell you the basic instinct of the dog. It will tell you what the dog was bred to do. Up until the last 150 or so years dogs were not kept as pets. If they didn't do their job they were either killed or left feral. The little dogs were bred to hunt vermin for the most part. I have Yorkies and I don't trust the Yorkies with the chickens. Now that doesn't mean that all the Yorkies are the same. I have 2 that are reasonably safe with the birds, and two that I will never trust. The other one is somewhere in between. I have 2 parents, and three siblings. I also have a Komondor. I would trust him with my life, and that of the birds lives. I had to teach him that though. He got one rather sharp lesson on don't mess with the birds, and 11 years later he is still bird proof. I have also had mutts, best dog we ever had was a Chow mix. She was bomb proof, and the best mouser I have ever met. I think some of choosing a breed or a dog is to figure out what traits you can live with, and what you hate. I have a very strong preference for long haired dogs, a lot of people don't. I don't care much for hunting breeds, most people seem to like them. I wouldn't own a Lab if I was paid to. I prefer extremes in sizes, and temperaments.
So those are some of the things you need to think about and answer for yourself first. The next is "Do you need the dog to be pure breed dog or not?" Do you want a shelter dog, or one from a breeder? Will the breeder take the dog back? Can you test drive the dog? I agree with ruth that not all LDGs are going to be warm and loving to the birds. Herding dogs on the other hand can be very nippy with animals that it herds. So you can't trust any dog just because of it's breed alone. It is a case of breed plus individual animal.
By the way I like the German Shepherds that ruth has. They look better bred than most. I was told a story about how years ago there was a AKC judge that liked the slanted lines on the breed. It almost destroyed the breed with all the hip problems. Okay I like the house too.