No, it's not an idiom, and I'm just making an hopefully educated guess here, but yes, crows are intelligent creatures, and they use their brains for "systematic thinking," e.g. by storing chunks of glass in a hollow trees so they can return later to inspect them for bits of food for survival. So when Midori brags that he chooses multiple choice answers by his gut or intuition, the other speaker says he has to have more of a plan and a system (like the crows) because his intuition isn't good enough. Hope this helps!
