Rooks causing havoc!

we have three bird feeders in our garden, with lots of different food types. 

The local rook family (5 or 6 birds) have taken a liking to our upper mealworm feeder, throwing it on the ground to spill out the food and also pulling out the water bowl. That’s our robin couple’s favourite mealworm feeder, as they wont interfere with the goldfinches, so I’m having to refill it everyday, which only encourages the rooks more! 

I like rooks and would like to keep them around so is there anyway I can build a feeding station that is more attractive to the rooks? maybe something shiny? Maybe something with a challenge to give them the fun they seem to be looking for?