There’s an interesting paper out titled, "Evolutionary Divergence in Brain Size between Migratory and Resident Birds". It’s interesting in that it is an example of a case where, big brains are not always better. Here’s what ScienceDaily has to say about it….
Scientists have known for some time that migratory birds have smaller brains than their resident relatives. Now a new study looks into the reasons and concludes that the act of migrating leads to a reduced brain size. Authors point to the fact that the causes could be due to a need to reduce energetic, metabolic and cognitive costs.
“For birds that travel a lot, exploring their surroundings produces more costs than benefits since the information which is useful in one place is not necessarily so in another. It also exposes them to more dangers. For these reasons we believe that for these species, their innate behaviour can be more useful than learned behaviour.”
I don’t find it a surprising result though. What is “better” depends on what your goals are. And I don’t see why more intelligence would necessarily be the “better” for reaching every possible goal, no matter what that goal is.