Train is a bit of a shorthand here, though. Basic operant conditioning probably won't cut it. But the idea itself came to me after encountering similar thread about crows on HN many years ago - both comments and referenced articles would contain personal anecdotes about human-crow relationships, and from those I gathered that it's possible to kind of befriend a crow (or a group), and teach them behaviors as a kind of play.

So, I don't expect it's easy to train crows like dogs and pigeons, where one person "pre-trains" them and gives/sells them to someone else. But I think it should be possible to "train" a crow for yourself - bond with it and have it voluntarily indulge you reliably enough that it's pretty much like training.