I have to disagree with the its not the breed issue.
It has ALOT to do with it.
Certain breeds have been bred to KILL LARGE ANIMALS.
Certain breeds have been bred to PROTECT ANIMALS and/or PROPERTY.
Certain breeds have been bred to RETRIEVE.
Certain breeds have been bred to KILL SMALL ANIMALS.
Certain breeds have been bred to be USELESS
Really thou, the breed is the most outstanding factor. You can get lucky but it is just that LUCK. Most people do NOT realize most older dog breeds have been bred to ignore livestock (The ones that didn't were killed) It's alot of the newer breeds and breeds made to kill rats, foxes, mink, birds etc that are the problem animals.
If you go with a protector breed (One breed to protect livestock) you are much less likely to have problems.
You need to realize a german shepherd is not made to hunt animals. Look at the name Shepherd. It is made to protect animals from all intruders, it is alert, it is intelligent. The same can be said of a golden retriever and lab. They are made to retrieve birds WITHOUT harming them. Most labs will just catch a bird and walk around with it in its mouth all day long without harming it in the least (The bird will think otherwise.)
While good training can go very far, it is not the final factor. The owners attitude helps alot, also raising the dog around the birds as a puppy helps.
You can train a dog it's WHOLE life, it only takes one bad day or your dog being jealous to set it off. If it doesn't have those tendencies to start with you are that much safer...
Bubba
PS Choose a breed made to protect and your much less likely to have worries later.