>>14959200 (LB)
You are forgetting the part where the black forest dwellers, farmers, loggers, artisans would capture and tame song birds.
So when do birds sing ? To communicate from within their cages to other captive birds is one reason. The bird farmers would allow them to mate and nest in captivity because the offspring was not conditioned to live in captivity until the third generation.
Since WWII they have been letting the sheep mate and nest in the captivity of the propaganda fueled media nest. This is our only chance to break free for a thousand years.