This looks great! I have never cared for Mausritter or mice, but this got my attention. Are the birds playable? If not, please make them playable. In fact, you should consider making a full game of birds, whether it's from Mausritter or your own game and you will have my full support! Keep up the great work!
Viewing post in Sparrows in the Snow comments
I've thought this over and I think a sparrow could be a character in Mausritter with a very simple caveat: they are able to fly so long as they have at least 4 spaces empty in their inventory. Sparrows pack light but make lots of trips back and forth for things they need.
I might consider a species document down the line.