Ripple of Birch Bark failed one too many times to bring back a kill -- not because he failed to catch anything, which would be more times than not, especially in the cold of winter. No, Birch decided his needs outweighed those of the Pack, and he was caught eating his catches before sharing them with the Pack. Multiple times.
He is now regulated to Pupsitting duty. This is not a punishment, although Ambercloud does hope that it might teach him to think of others. He just cannot be trusted to bring things back to the Pack, so better he just never leaves at all.
