I really love this piece! The pose is very well done and I love how the brown colors in Birdsong's pelt are mixed. And that tail, oh my gosh. The bird looks really nice, too!
Ravenpaw and Birdsong both seem like pretty lithe and agile cats, so I was thinking of a name to emphasize that... I couldn't find any birds of that color though. Maybe Minkface/foot/step? They're pretty dark brown and sometimes have a white patch, and they look pretty slithery to me. |D Perhaps Coalfoot/tail/face because as you mentioned, certain parts of his body would be darker than others, so maybe you could highlight them?