I have a bird feeding tree in the garden with three seed holders, I fat and one peanut holder. The tree is not designed for crows and in fact their are intricate metal leaves and flowers that prevent them getting a claw hold. However, they worked out how to perch on a round metal ring and bash their heads against the seeders to release seeds to their mates waiting on the ground below.
I spent time working out how to remove this access point and in the end we rearranged the tree arms so that none were within butting distance. Then they worked together. Two would lift the handles of the individual seeders, lifting them over the long hooks and onto the ground where they spilled out.
So I wired the seeders to the tree. Which infuriated them and we could watch as two or three would gather to work out the problem. Clearly whilst we were away they solved it. I came back to find they had untwisted the wire securing the seeders (several twists) and thrown them to the ground.
They are very clever and part of my attempts to thwart them, is to see how they solve the problem. Here is another crow who has mastered a complex set of actions to get the treat.