The various members of the Corvid family are pretty smart. The fact they can live a long time, compared to some other birds probably gives them a better opportunity to learn. Although there are doubtless some thick old crows who are just lucky..
The crows in Bodmin, Cornwall, worked out how to tip over dustbins. A workmate was fed up with his dog getting the blame so he got up early one morning and saw a flock of crows working along the street testing bins to see which ones 'wobbled' by landing ono one side of the rim. Sloping and uneven pavements (sidewalks) probably helped with this.
The more heavily filled bins were stable and were left alone..
But as soon as they felt one which moved beneath their feet they'd call the others, who would flock over, land anywhere on the lid, and then shuffle around to add their weight to one side until the bin tipped. If the lid fell off and spilled the contents they would then revert to squabbling disorder over which had what.
It the lid stayed on they would have a few attempts at pulling it off, levering with theor strong beaks, but never spent wasted too much time trying.
I assume, possibly wrongly, that at some point a crow knocked over a nearly empty bin, was seen by others doing this, and they realised the potential. Whether they reasoned it out or just learned from the first example we may never know. After all, how did sparrows 'learn' there was cream to be drunk below the foil caps of old fashioned milk bottles? Did one of them just attack his reflection in a silver cap, believing it to be a rival, and thus accidentally discover the treasure below?
