Crows are awesome though, I'm not trying to put down their intelligence, haha. I just wanted to point out that neither deeper reasoning nor ethics is required to explain this phenomenon. One of the researchers in the article said that he had never experienced the gift giving, even though he also fed crows often. That to me makes it more sensible to believe that it's just a meme that developed by chance
But crow gifts are not guaranteed. "I can't say they always will (give presents)," Marzluff admits, having never received any gifts personally, "but I have seen an awful lot of things crows have brought people.
I think the article (and probably the podcast? haven't listened yet) make too big a deal of this. We don't know that the crows realized that the lens cap belonged to those people. Perhaps they just saw it as another neat thing to gift. Perhaps they smelled the family on it, and just returned it to a place that smelled similarly.
For many birds though, it's nowhere as good as their hearing or eyesight.
Can you do that?
https://books.google.de/books?id=Z7g-BAAAQBAJ&pg=PA105&lpg=P...
Maybe not, but then, humans have a pretty poor sense of smell compared to lots of other animals.
Crows / Ravens are the only creature aside from Humans who perform meta-tool use. They can use tools to grab tools to accomplish a goal. In many ways, they're smarter than (non-human) primates, and are probably the 2nd smartest animals on earth.
https://en.wikipedia.org/wiki/New_Caledonian_crow#Meta-tool_...
Birds in general are pretty smart (see Pidgeons, Parrots, etc. etc.) However crows / ravens are on a completely different intelligence level. Crows break nuts by dropping them on the asphalt... timing their drops during red lights so that traffic doesn't hit them.
Besides, gift-giving is seen in far dumber animals than crows. Dogs, Cats, Penguins... they don't have the intelligence of Crows but they understand gifts and social situations.