Maybe it's like how we (most vertebrates) have blind spots built into our eyes due to a quirk of evolution, but some animal like squid etc don't... because their eyes have better cable management.
Birds, on the other hand, have a disting evolutionary advantage in making their brains as small and light as possible.
To me, this implies bird brains are likely to be much more efficient, both volumetrically and energetically. That's the more fascinating angle, IMO
> Birds, on the other hand, have a disting evolutionary advantage in making their brains as small and light as possible.
I'm not sure about that. Not all birds are as clever as crows. Who knows if a few less grams of neurons is worth the "IQ" loss, and conversely who knows if a few more grams of neurons makes a difference in terms of survival? Not to mention that these animals must also have vestigial or ridiculously expensive organs or functions (e.g. peacock's feather), so maybe they are not so sensitive to weight or energy consumption. It is difficult to measure.
I've long been puzzled by the fact that if intelligence was such a big advantage - almost like cheating in our case - why is it not common? Well, for one thing we wouldn't have struggled a lot more to get to the top of the food chain. But Evolution is the process of adapting to an environment, and sometimes it selects what is "good enough". In a way flies are far more successful than us, because there are millions of flies for each one of us, and they are more likely to survive a planet-scale catastrophic event. Sometimes brute-force reproduction works better than more neurons.
If another mass extinction occurs, we are toast (See "The Ends of the Earth"). Relatively minor ecological changes may even destroy us. Sapience has not yet proven to grant any long-term advantage.
(Assuming life arose on Earth only once. That seems like a convenient moment to start the clock.)
Their brains also aren't structured similarly to ours in a gross sense, although the so-called "mushroom bodies" do appear to serve similar purposes to our cortical "gray matter," and if I recall correctly, there is some sense that connectome complexity scales proportionately with complexity of behavior, though I'm not sure how well this has actually been studied.
On a similar note, though their primary eyes aren't constructed at all like ours, they do nonetheless exhibit a "foveal" area of highest detail and resolution, in the regions of their eyes where it does them the most good - namely, ahead and below, the latter aiding in manipulation with palps, mandibles, and the front pair of legs. That's not quite the same as a brain per se, of course, but it does also point to the adaptive constraints under which evolution has occurred: as flyers who construct their own nests and who regularly must travel long distances to find all the resources a colony needs - or, as peripatetic mammals who came up grazing as much or more as hunting and use tools - good eyesight, memory, and dexterity are all very valuable, and thus it isn't a great surprise when such species that become successful on a cosmopolitan scale show extensive development of these traits. The infrastructure on which the trait is built may be independently of interest, but not being able to understand how such a small infrastructure gives rise to such global traits isn't an excuse for ignoring the exhibition of the traits.
In light of all that - plus the anecdotes that such a close and friendly interest in wasps would tend to yield - I've tended to think of intelligence in this sense, or capacity for same, as sort of "holographic" in concept: if you make a hologram on film and then cut it in half, what you get is not two halves of a hologram, but two complete holograms, each with lower resolution than the parent. I think brains scale the same way, such that what you get with a much smaller brain is not so much less breadth as less depth.
I don't really have a clear formulation of the concept, or not yet at least, but hopefully you can see at least a vague outline of what I'm reaching for. Or that I do, at least! Maybe we could think of it as the anthropic principle shorn of human chauvinism, if you like.
The caloric enrichment of food by cooking probably can explain this as well. We got smart enough to cook, which gave us more energy from less food to power the brain. At that point, the evolutionary advantage of metabolic efficiency matters less. It allowed early humans to continue developing on the same path, probably increasing brain complexity somewhat over time while not focusing as much on energy.
But I'm no biologist. I'm just guessing.
Maybe the ours are getting more efficient too.