The end Thermocene boundary was a three million year long slow death, taking the majority of all life with it in a series of repeating extinction events worse than the world of birds had ever before known.

But now, 178 million years post-establishment, it is over, and the barrage of oppressive heat, ice ages, constant volcanic explosions, and lack of oxygen have come to an end. Puffgrass is the first plant to take advantage as new land returns to a habitable condition; spread on the wind its its fuzzy seeds by the billions, it takes root in every available crack of dried lava as a pioneer species, and soon forms vast stands thousands of miles across, from one side of the continent to the other. It snuffs out light, preventing competitors from taking root. Never before in Serina's history has a single species so totally dominated the world.

It is followed, just a few thousand years after the climate becomes stable, by mucks. One of the more tenuous survivor taxon of the extinction event, these creatures endured due to a high temperature tolerance, low caloric needs, and ability to survive on seawater and find food in such unappetizing things as extremophile mats of bacteria growing in a tepid, stagnant sea. Now a green wave of edible vegetation draws them in from hostile coasts, and a terrestrial-adapted species of muck has arisen. Over the last hundred thousand years, they have exploded in number to over 5 billion - the most numerous single species of bird on Serina since the initial introduction of canaries. Called the swarmuck, it is a disaster taxon: a species that exploits the instability of an environment immediately after an extinction event reduces or removes former competitors. Swarmucks are neither smart, nor fast, not especially efficient feeders. But they can walk a long ways, can eat a lot, and they can have a ton of babies. In a world with no predators big enough to threaten the adults, endless food, and nothing else to significantly compete over that food, this has been enough to enable their incredible spread across the new green world from coast to coast.

Swarmucks aren't really social animals, but when there are billions of you, you must get used to close quarters. Such an abundance, though it seems to indicate a winning life strategy, does not really benefit the individuals. There can be too much of a good thing, and now the swarmuck is becoming a victim of its own success. Overpopulation means that even as food does not run out, their social behavior becomes abnormal as they are constantly on top of one another nearly all of the time. Males, slightly larger than females, are often greener and have a pink dewlap. They are not gregarious, and are inclined to fight over mates, displaying their color to attract a partner. Such a high population means they are fighting continuously, and have little time to focus on females at all. Battered and bitten, they are often succumbing to infections over long time spans with nothing to cull the weak, old, or sick. Females, though less put off by each other, must select damp, sheltered places to nest and bury their clutches of eggs, but so many exist that breeding grounds are trampled to mud as millions of mothers-to-be dig holes on top of previously laid nests, destroying the eggs of those which came before them. With the climate now in a stable but unusually warm and damp hothouse cycle, there are no seasons, and so breeding goes on continuously. In some places, the nesting grounds are so crowded that less than one in 1000 eggs successfully hatches, and most surviving chicks are inadvertently crushed by the herds of adults that prevent them from fleeing the nests and finding safety in the grasslands.

Swarmucks now sit at the cusp between a boom and a bust. Their population is unsustainable, and with nothing else to limit them, they become their own worst enemy. As long as no other animal exists which can push into their niche, they simply rebound after calamitous population declines of up to 99% every few centuries. But now, 500,000 years after the end of the extinction event, that is changing. There will soon be seasonal changes again, bringing food scarcity. The mucks will soon face the appearance of tribbethere predators which begin hunting them and their young, and waterfowl will increase in number, for they can better migrate between flushes of green vegetation and avoid overgrazed land as millions of swarmucks will starve.

To be a disaster taxon is to live short and fast. They have taken full advantage of the chaos between eras in a way few animals could manage.

But now the Pangeacene is here, and their reign of dominance will soon come to an end from which they will never recover. In less than 100,000 years, the swarmuck - now the most abundant bird of all time - will be extinct.

And soon after in its place, not one, not a hundred, nor a thousand, but millions of species will prosper in a new, golden age of life. The return to stability is a long, slow climb from such a devastating interim, but like the tortoise and the hare, those slower to get there in the beginning will come out the real winners in the end.

Already the swarmuck faces new threat. From the grass it erupts with a flurrying flutter of wings, but this hunter does not fly: it runs, the sound of lightning quick steps as it pursues its quarry falling like light rain on the grassland. To a nearby swarmuck, it hardly makes a difference, so quickly is its new, mortal enemy nearly on top of it. Not adapted to run quick or used to pursuers, what now comes after it is a recent arrival from the northern sea shores. A shorebird-like shrieker, a hardy survivor of the end-Thermocene boundary, has moved inland with the calming climate. In response to new foods to be found in abundance in its new range, it has grown in size to a height of almost 25 inches, roughly equaling the muck. This is a black-crowned tracker, a member of a new clade of terrestrial predator birds, the wolf shrikes. And it is the largest, and deadliest of all. 

For a brief period in this changing world, the tracker - though weighing only 12 lbs - becomes an apex predator. They are spreading southwards; having colonized North Anciska, they now cross the narrow land bridge to Striata. From here, the entire supercontinent will be theirs to claim, a superhighway of inviting grassy meadows, filled with prey naive to danger. Other wolf shrikes are flying birds; they hunt only small vertebrates like tribtiles, and focus mainly on arthropods. The black-crowned tracker specializes in big game. Running up to 32 miles per hour they more than triple the swarmuck's top speed and easily run them down. Their wings are too small to carry them upwards but provide balance at high speeds, while their lengthy tails become a rudder and enable instant turns. Younger ones are yanked off their feet and pinned down; larger adults may be forced down as this agile hunter leaps onto their backs, grasps with it talons, and flutters its wings to hold on until its victim collapses. It always kills with a clamping bite to the throat and suffocates its prey, like a lion, and in a world with little other competition, this is the sort of niche the tracker fills as the predator of herds of grazers.

But the tracker is not as different from the swarmuck it slaughters as it might wish to think. It, too, is a very early comer to the new world of the Pangeacene, and its dominion over this world will not be permanent either. As trackers spread south, eating their fill, they will one day come across other hunters, bigger ones, working their own way across the landscape. Creatures the likes of which the tracker has never before seen, and is no more used to than the swarmuck is to itself.

The tracker must not grow too confident, because nothing lasts forever - and the Pangeacene is no longer an age belonging to the birds alone.