Bird-brains are generally much more efficient that mammal brains. It's the same as the lungs. Mammals are just better at not eating so much and they can stand poison better.

So even if I can outdrink Lilo any time, she can outdrink even a big bird, I think. Not that any bird would ever touch something with alcohol in it... Maybe their problem with poison only has to do with their lungs. Birds have a problem with gases.

But: Small brains have nothing to do with being stupid. It's not like a tiger need a bigger brain than a cat, but they still have one bigger than ours (or something? It's big anyway). And small humans aren't stupid because of that.

On the other hand: A big brain makes you slow. It takes longer time for signals to travel from one part to another.