Because it’s not their trash, the disgusting humans should pick it up
They misspelled human.
Maybe offer them better incentives than the literal version of the go-to metaphor for not getting paid well enough.
Really, though, what I can’t stop thinking of is my cat. Things have gone a lot better with her since I switched from trying to train her to do some things and not do others to just communicating at her level; I indicate my own intention to do something and let her make a decision based on that. For example, it took three occasions of counting down from five before closing a door for her to develop the habit of either crossing through at the last second or leaving contentedly after it closed instead of scratching at it again.
If you want crows to do something, I think that’s the way: become predictable for them and let them choose how to proceed. I think if you walked the same daily route and consistently picked up litter and left food in its place whether they were the party that brought the litter or not, then they’d puzzle out how to game that.
I think this is the point the article is getting at. Crows know it’s us not the machines (which are unreliable).
Kevin is smart enough not to throw his trash on the ground. Why won’t he?
