I've thought about teaching them this, but ultimately I decided against. While they may find unclaimed loose change for you, they could just as easily figure ou

I've thought about teaching them this, but ultimately I decided against. While they may find unclaimed loose change for you, they could just as easily figure out a scheme to distract and rob some poor beggar or busker, and you wouldn't ever know. There's probably some kind of crow-to-crow "these are friends, these are enemies" abstract communication, but I don't think you'd have much luck communicating the concept "to me, humans are friends, so don't rob them on my behalf" across the species barrier.