Out of all the sapient species that have lived on the planet, all of them except the woodcrafters have been birds. One reason this that they likely had a head start over the tribbetheres as they were already somewhat intelligent terrestrial animals by the time they were put on the terraformed world, but another reason likely has to do with their brains. Birds have a brain structure that makes them more space and energy efficient than Earth mammals which would make it easier and less physically and metabolically costly to develop sapience.
The aukvultures are scavenger birds but they possess fully feathered heads and necks, whereas scavengers like Earth vultures are bald in those areas to prevent viscera from sticking to them when they have their heads inside a carcass. However, there are two explanations as to why they wouldn't need bald heads despite their diet; one is that they are described as having powerful, bone-crushing beaks so they would simply be able to break a carcass into smaller pieces without having to stick their heads inside it. The other is that they evolved alongside the Sea Stewards whose leftovers would already be fairly fresh and already in pieces by the time the aukvultures would have gotten to them, eliminating the need to get inside the body cavity in the first place.
How did chatteravens get to Serinaustra to diverge into the bogglebirds? Brighteye mentions that he can't fly too far out to sea due to the presence of "bigger wings with sharper beaks", but the subsequent collapse of the ocean ecosystem and by extension the extinction of many of its avian predators means that a trip across the ocean is far more survivable than it would've been before, on top of a defrosted Serinaustra having far more food to eat.
The Late Ocean Age may not have been the first time the observer intervened. Countless other disasters, triumphs, and lives may have already been rolled back and erased by the observer. How many civilizations and people have not only gone extinct, but have been obliterated from history as we know it because they threatened the stability of life on Serina? How many times has Serina been sterilized and restored? The Thermocene came awfully close...
