I clipped a duck today that sailed out we'll over 200 yards and then folded up dead. Dog didn't see it so I sent him blind and he made the retrieve.
Doesn't always happen but it's nice to have a dog that will do it if necessary.
One thing though, don't send a dog on a blind retrieve if the bird is wounded and your not sure it didn't run or swim away. If the dog doesn't come up with the bird when being handled it will learn not to trust you. Always make sure there is a bird to retrieve......that's their reward.