Tom Cox @cox tom
Almost certainly the best thing I wa ever told about owls was when I met an owl handler and he told me that the wild owls in the sanctuary where he worked worried about the tame show owls there and sometimes stopped by to leave them shrews and mice as presents.
Total size is secondary.
Number of neurons / brain size in comparison to total body size is a common metric used to predict intelligence. Bigger bodies need more neurons dedicated to control and coordinator muscles and organs.
Besides the excess neutrons, it helps if the animal frequently have free time and energy available after hunting for food as well as not needing to constantly watch for predators.
Even then it’s just a vague correlation, not a strong prediction.