https://www.scientificamerican.com/article/pigeon-neurons-use-much-less-energy-than-those-of-mammals/

Pigeon Neurons Use Much Less Energy Than Those of Mammals

Weirdly efficient neurons power birds’ dense brains

.. . .

The intelligence of some kinds of birds - esp covids
and parrots but not limited to those - is extremely
surprising given the very small size of their brains.

In part, the reasons for this are now clearer. Bird
brains use narrower neurons, which means more of them
can be packed in, plus narrower usually equals faster.
On the whole, a pigeon brain packs a third more power
than a mammalian brain of the same size.

However there's an IMPORTANT co-factor ... more and
faster neurons in the same space mean HEAT, the energy
demand and heat production is larger. Avian neurons
are much more efficient than mammalian neurons - more
computing per calorie. They also may be "wired better",
though there's no immediate evidence.

Birds, flying birds, need to pack IQ into a very light
package. Darwin would favor such adaptations.

If human brains could be made this compact, fast
and efficient - not "impossible" given future
genetic tech - would average IQ be today's 300 ???

Oh, as birds are technically dinosaurs ... did those
pea-brained dinos we do often deride ALSO pack a lot
of IQ in their heads ? So far I'm not aware of any
well-preserved dino brain being found. No "dino tech"
either - but then hominid tech was very slow to
develop as well. Even 'humans' (a fuzzier term than
you'd think) did not exceed the tech of the earlier
family members for a very long - like 100,000+ years -
time. IQ does not necessarily mean tech evolves
anytime quick. Other factors play into that,
especially 'civilization' ... a social environment
where small tech ideas can be passed along and
refined through generations.