I learn something every day, I knew they were smart but not this smart.
Intelligence of a Rook
In captivity, when confronted with problems, rooks have been documented as one of several species of birds capable of using tools. Rooks learned that if they push a stone off a ledge into a tube, they will get food. The rooks then discovered they could find and bring a stone and carry it to the tube if no stone was there already. They also used sticks and wire, and figured out how to bend a wire into a hook to reach an item. Rooks are as clever at making and using simple tools with their beaks as chimpanzees are with their hands.
In one experiment, a rook was placed near a tube of water, with a worm floating on top of the water, and some rocks next to the tube. The water level was too low for the rook to reach the worm, so it placed rocks into the tube until the level was high enough.