Doin’ a quacking
This dog seems to be a strong believer that you can be anything you want to be, as long as you work hard for it and have a strong self-belief in yourself. So he decided to go for it and fulfill his wish of becoming a coot.
It is the 21st day and he is not barking, just quacking. We see he has made new friends and he is getting along well into the environment, and the birds have accepted him as their own. The identity is enclosed until someone throws a ball near the lake, then his truth will be revealed.