On Intelligence
Since the evolution of life on Earth, there has been an observed tendency towards the evolution of animals with more complex brains. Neornithe birds - passerines and their sister clade the parrots in particular - have larger brains and can be inferred to be more intelligent than the very brightest non-avian dinosaurs before them, the Troodonts. Troodonts, however, were themselves bigger of brain than any theropods before them and and these in turn still had larger brains than the lizard-like reptiles they evolved from.
Certain modern Earth mammals are undoubtedly the most intelligent synapsids ever to live. Carnivores and several groups of ungulates are demonstrably clever, and among placentals extremely high intelligence has evolved independently in primates, elephants, and dolphins. Before the end of the Cretaceous, there were no known animals as intelligent as even a dog or a pig. Just sixty-six million years later, not only were there dogs and pigs, but animals whose intelligence approached sapience, and not from one group but several, from two widely unrelated clades, which peaked of course in the primates with the evolution of humans.
The fact that a great many animals have not become relative geniuses in the time span in which ourselves and our avian, cetacean, and elephantine kin have done is of course proof that this trend is far from universal. For many animals a larger brain is only a burden, requiring lots of energy to be maintained, and survival is possible with the same more primitive equipment that their ancestors evolved tens or even hundreds of millions of years ago. For other creatures, though, intelligence is the answer, and intelligence, it seems, breeds further intelligence. During the Cenozoic multiple animal lineages simultaneously began approaching perhaps the ultimate endpoint of intelligence - sapience. Only one reached it - ourselves - but the potential was there for others.
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Serina is an interesting world on which to observe the progression of intelligence, for its colonists included one relatively advanced animal group - a passerine bird - and many fairly primitive ones - invertebrates and ray-finned fish. The differences observed over hundreds of millions of years between these groups have been very dramatic, with one group of fish - the tribbetheres - and one group of mollusc - the snarks - in particular having become very intelligent in comparison to their ancestors. But there has not been as dramatic a continuation of this trend among Serina's birds, and it can only be inferred that is is because passerine birds are, relatively speaking, already a highly intelligent group which perhaps have already reached the peak of efficiency in their smartest Earthly forms, where a brain of any larger size is not advantageous except in extraordinary circumstance (circumstances like those which led to humans.) Conversely, more than one group of birds upon Serina has lost intelligence, developing smaller and simpler brains than their ancestors, further proving that life does not automatically become more complicated and intelligent over time; though it certainly can, it will not if conditions do not require it. These notable exceptions - in particular those species which have lost their endothermy such as mucks and certain changelings - notwithstanding, though, it is demonstrably certain that overall intelligence of birds on Serina in the late Pangeacene is greater than that of birds on the whole on Earth in the Holocene. Though Serina has not become a world of many different sapient bird cultures, most birds which occur there in the Pangeacene are more intelligent than the ancestral canary. Early radiations of dim-witted herbivores occured in the vaccuum of Serina's empty ecosystems in the Hypostecene, but this was not the trend just a few million years later by the Tempuscene, when a more varied ecosystem of predators and threats weeded out the dullest bulbs.
Though a canary started off pretty far from a crow, intellectually speaking, the underlying structure of its brain was the same and it carried within it the potential to become crow-like quite readily. Multiple lineages of intelligent corvid-like birds have existed on Serina since the late Hypostecene, including forms capable of rudimentary tool use and cultural behavioral transmission. While truly gifted brainiacs that rival keas and New Caledonian crows are still relatively rare, they can be found among groups as distant as the sparrowgulls, bumblets and ornimorphs. Indeed, a more general intellectual prowess comparable to certain smaller corvids such as jays and other parrots would now be considered typical for a wide variety of bird lineages including almost everything except previously noted examples of ectotherm birds, most softbill birds, some primitive bumblets, and true galliwalt-descended waterfowl, which are the most primitive of birds alive in the Pangeacene and have retained a relatively simple chicken-like brain.
In very basic terms, extraordinarily few birds on Serina have ever evolved which are smarter than the smartest of Earth birds, but similarly intelligent birds have become more numerous. Indeed, in over two hundred million years only one bird is known to have ever clearly surpassed the most intelligent Earth birds intellectually, and it has done so only very recently. At the very end of the Pangeacene, approximately 240 million years after the very first birds were introduced, a new tier of bird sits at the threshold of something potentially groundbreaking.