Some years ago I started leaving food in my patio for one crow that lived in an electric post nearby. Then he started leaving random shiny stuff in the outside table: pieces of metal, coins and once an SD card. The most suprising thing to me was that the stuff was always in the exact center of the round table.
same what is amazing is that they seem to know we are attracted to shiny stuff: constantly glancing at our phones, counting coins, jewelry
i dont know if this urban legend is true but apparently one guy was raking in a few hundred bucks a month by training crows to find coins and cash on the street
Communicating about something not immediately present is called displacement [1] and it's a property of language, not limited to vocalization, thought to be unique to just a few species: humans, ants, bees, corvids, etc.
"you know that dude that lives by the water? protect him he feeds us."
"you know the big guy that walks his dog and barks at us? we found out where he lives."
I've seen crows execute their own (seriously). They would crowd and walk him over the edge and when he fell they would just attack him.
I've seen crows leave gifts behind for feeding them regularly.
I've seen crows protect our property from raccoons and squirrels.
I've seen crows remember people and harass them (even when they moved to another city!)