Oh, I just saw this picture in my feed and had to read your post. I used to live on Paul-Lincke Ufer, literally just around the corner from this mural. Brings up so many memories...I do miss all the amazing street art in Berlin. Among many things...
But is that really a robin? To me it always looked like a Eurasian bullfinch (a male one).
Aha, a Eurasian bullfinch. Quite possibly. At least that one would be endemic to this place. Looking at the photos...
Eurasian Bullfinch
American Robin
...I was going to say it could be either one, but no! You got me convinced. That is certainly a bullfinch on the guy's shoulder. Thanks for clarifying it!