> Even when humans have a friendship—or something that feels like it—with a crow, the relationship happens on the wild animal’s terms. They visit when they want to, and they may disappear from our life suddenly.

It goes also the other way around. I do not leave a note to my neighborhood crows when I move town.

I think that it has nothing to do in which terms it happens but the communication barrier. It is very possible that the crows signal that they are leaving for good but we are just missing the message. And my reason to not leave them a note is because they cant read, if they could I would.