For example, I recall a documentary showing a species of crow dropping snails onto rocks to crack the shells. The scientists in the program claimed that this behaviour was a unique development particular to a small colony of crows at the remote island location where they were filming. However, I see crows and gulls do this regularly in my bustling neighbourhood. To notice, it is only necessary to be a little more observant than the average zombie.
The idea that only these crows, of all birds, fly up with things and drop them to break them, has, I guarantee you, never appeared in the scientific literature. It couldn't, it would never get past the peer-review process. The phenomenon is well-known and has been studied in detail in many species.
I suspect that either you, or the makers of the documentary, have misinterpreted a statement to the effect that out of this particular species of crow, only this insular population exhibits this behavior.
As you point out:
To notice, it is only necessary to be a little more observant than the average zombie.
So people
whose job it is to study bird behavior --- they would have noticed, yes? Like, hundreds of years ago?
™ Version 4.2