Depends on the bird.
Discussion
Not the squirrel? Lot of different squirrels out there.
Your question is too vague. Birds come in thousands of different species. I bet you could find a bird smarter than the smartest squirrel and another one dumber than the dumbest squirrel.
For example I'd say all crows are smarter than squirrels and all chickens are dumber than squirrels.