The Jadeplain is western Ailuropia's warm subtropical grassland, bounded by the erosion-resistant shield of Quartzkarst along the coast and the vast alluvium of the braidwaters in the continental interior. To the north and south, the twin mountain ranges support steep forests that fade into foothill savannas, before finally giving way to a completly open lowland, with just a few scattered trees near sources of permanent water. The hills of the lowlands are gentle and rise only a few meters above the water table - shallow enough that numerous plant species can tap into it with their roots, but deep enough to leave lots of aerated space for burrowing animals. The biome gets its name from the abundant jade skystalks that grow here; they compose up to 80% of aboveground plant biomass in summer. In many ways, this means the Jadeplain is a remarkably simple ecosystem, with fewer distinct niches than even other grasslands. However, its fauna is just as diverse as those of other, more mixed-family grasslands. This is due to the work of ecosystem engineers among the ranks of its herbivores and carnivores, whose actions prevent the collapse of the Jadeplain into a homogenous landscape of just a few dominant animals. Each guild (a loose association of species with a similar dietary niche) is regulated by at least one engineer species that forces a balance between the several members of that guild.
The Grazers
In any grassland environment, it's no shock to learn that the majority of megafaunal biomass comprises grazing herbivores. With one clade of grasses dominating the landscape, there is no opportunity for different grazers to exclusively specialize on different types. Though they may have their preferences, all grazers on the Jadeplain must in some way compete for this one resource. Yet competitive exclusion does not reign supreme; physical and behavioral adaptations among the grazers have allowed them to coexist by feeding in different ways, in different spots, and at different times. These distinctions don't rise to the level of separate niches, as all the species are ultimately limited by a single resource, but they carve up that resource along complex lines of geography, territory, and microclimate.
Since basket-grasses (including barrel-grasses) make up most of the remaining 20% of plants, the Jadeplain supports multiple species of basketbucks, though neither is able to fully specialize for its ancestral diet. Instead, they split their feeding about evenly between baskets and jade skystalks. They differ from one another in size, speed, and social structure, and they diverged from one another at the very beginning of the Arthrocene, so they bear little physical resemblance to each other.
The Barrelbank (Doliophilus ripariensis) grows to about twice the mass of a muskrat and lives in a similar environment. It belongs to the barrelbuck tribe, a clade of cryptic microungulates that don't run far or fast, instead relying on burrows or vegetation for cover. In drier habitats, the barrelbank's relatives can construct kilometer-long tunnels to deliver themselves to the best feeding sites. Here, tunnels must be more modest, rarely running more than a few tens of meters. They consist of two to five openings close to a stream or pondbank (preferably tucked into the roots of the few trees in the area), a dense network of runs and food storage chambers, and a single central den where the pups are raised. Several females (usually related) typically share a burrow, and often a mate as well, though multiple unrelated males can occasionally coexist in a large enough colony. The whole group, save for the strongest and most socially dominant pair, leaves the burrow nightly to forage, making the trek uphill to reach the open grassy areas. This means the biggest, toughest male and female have the job of staying and defending the pups, who are born relatively altricial for Muridiungulates, taking as long as two weeks to emerge from their den. In the event of a predator attack, they may seek to sacrifice other members' offspring to save their own. However, the other barrelbanks may notice this and depose the dominant pair, so they are incentivized to work for the safety of everyone.
Basketbeests (Monoungulomys) occupy the other end of the size spectrum amongst basketbucks, with six species worldwide growing to an average of 250 kilos. The Jadeplain species, which is relatively uncommon with only around 50,000 total individuals, can double the typical size of its genus. Known as the Jade Switchbeest (M. occidentalis), this giant grazer lives in small harem-style herds with up to 25 adult members. Only one of these may be an adult male, while the rest are his mates and offspring. There are no bachelor herds, as adolescent male survival rates are simply too low. Unlike other "beest" Muridiungulates, this species throws its young males out of the herd as soon as they are weaned, typically less than 60 days after being born. This is due to the actions of female herd members, who are intolerant of other females' young. This is because females in a jade switchbeest harem are usually unrelated; in other basketbucks, groups of related females care for each other's young cooperatively. Of course, the only way for a herd to remain composed of unrelated females is if they also disperse at some point in their lives. This comes much later, at the onset of sexual maturity around their third birthday. To avoid breeding with their own fathers, they seek out a new group, unless their natal herd has recently seen a change in leadership to an unrelated usurper.
Switchbeests have the highest combination of speed and endurance of the Jadeplain's herbivores. They can go from zero to sixty-five kph in under two seconds, and this speed can be maintained over a distance of around 5 miles before stopping to rest. At a trot, they can cross a hundred kilometers a day, only slowing to a walk when they need food or water. Humidity is high throughout most of the year, and as the largest grazer on the Jadeplain, the switchbeest is the prime target of many biting insect species. But the switchbeest has one defense: it gets its common name from its swatter tail, which ends in a bristly tuft of 3-millimeter-thick hairs. It is held up in a loose coil, for it grows as long as 250 centimeters - almost a meter more than the switchbeest is tall. Propelled by a bundle of muscles at its base, it can reach anywhere on the switchbeest's body. It is not, however, a good weapon against predators or rivals, as it can't break skin or inflict significant blunt-force damage to anything larger than a kilogram or two.
The same cannot be said of the facial ossicones of the Battering Ox (Aepyceromys ubiquitus), which grow directly out of the skull, unlike Giraffids of Earth, whose ossicones developed within the soft tissue and later fused to the head. Early in development, the frontal bone of the battering ox (and several other related species descended from the impalox) "folds" in on itself, creating a ridge in front of the eyes. The center of this ridge is reabsorbed before birth, while the outer corners migrate up the forehead, ensuring they don't obstruct the eyes. By the time the ox reaches its full size - 100 kilos for females or 130 for males - the fur on its cones will have long since worn off from repeated use, leaving only a layer of skin atop the bone. When they're young, however, battering oxen have fuzzy eyespots on their ossicones, pointing upward to startle any predator that looks down upon them in the tall grass. Mature females have slightly shorter and sharper cones, better for fending off carnivores, while males' are bigger and blunter, making them more useful in nonlethal intraspecific combat.
Battering ox herds number in the hundreds of thousands, each one patrolling a wide swath of the jadeplain, usually demarcated by rivers or changes in elevation. They are the chief ecosystem engineers among the grazing guild, keeping all others in check. For example, the switchbeest, with its larger size, has the most efficient digestion of all jadeplain grazers. Left to their own devices, they would decimate the landscape, keeping grasses down to a thin layer of turf and outcompeting most other herbivores. This doesn't happen because the oxen keep them on the move; predators constantly follow the great herds, so switchbeests always keep their distance. This means they can never stay in one place long enough to keep other species permanently suppressed. Similarly, the barrelbank's population is always on the verge of swelling to pestilential numbers, as its protective burrows and cooperative society afford it a reproductive rate unmatched by any of its competitors. However, with so many mouths to feed, its colonies can collapse quickly when food becomes scarce, such as when a herd of oxen passes through the area.
Like the switchbeest, the Great Apteroo (Macropodornis gigas) avoids battering oxen because of the increased predator pressure in their vicinity. This 150-kilogram ouchwing also steers clear from large congregations of animals because it needs open, unobstructed space to hop efficiently. With no obstacles, it cruises at 30 kilometers per hour, traveling in mixed-age, mixed-sex groups of 5 to 25 most of the time. It crops long stems of skystalks just above the ground line, then works its way up the stalk like a multi-meter-long noodle, using its nail-clipper-like beak to cut the tubular grass into swallowable chunks as it snips its way along. Though it may be the largest of the pouchwings, no apteroo can measure up to the Western Struttio (Ornatocaudornis velox ailuropiensis), which eats in much the same way, though it first bends the stems down and starts from the top. This is a different subspecies from the struttios found throughout the rest of the world. The smaller vulgaris struttios of eastern Ailuropia gave rise to the Abelian and Loxodian populations within the last 50,000 years, but they split off from their giant western counterparts long before that, more than four million years ago, though interbreeding continued until less than a million years ago. Growing to a third of a ton, the western struttio narrowly outweighs the biggest vulgaris individuals of the Loxodian savanna. Its herds are larger and more nomadic, growing into the millions, but they travel far and wide across the western two-thirds of Ailuropia. At times, there may be none passing through the jadeplain at all, especially in late winter, when the nesting season starts and struttios head further inland to the braidwater rookeries.
The Abelitherian whiskerwig first evolved a world away from the jadeplain. The species originated in the southern half of Abeli, where its ancestors had lived for over ten million years. Though whiskerwigs primarily feed on terrestrial vegetation and need dry land to burrow, they've crossed the globe using waterways. The long hindlegs of this species are built for a hare-like bounding gait, so they move in tandem, with only a limited range of independent motion. In water, this allows for a powerful dolphin-kick stroke, while the forelimbs are held against the sides of the body, serving only to help steer the animal. With this streamlined movement, a whiskerwig can make headway against a current of nearly 8 kph. Of course, only some populations swim regularly; those in the snapscrub hardly bother, even when occasional flooding allows it, because little of their preferred food grows in such temporary pools. But anywhere with permanent standing or flowing freshwater is likely to see near-daily visits from the local whiskerwig population. In addition to grazing on land, this rat eats a variety of aquatic grasses, especially at times of year when terrestrial ground-cover is limited. During the early spring, turfgrasses are mostly dormant, just beginning to send out their first aboveground shoots. Likewise, by the end of autumn, these grasses will have gone to seed, either dying off completely or at least back to their rhizomes. In some lakes, though, the spring and fall turnover events bring flushes of growth that allow the whiskerwig to compensate for the lean times on land. During these periods, young individuals routinely use waterways as a dispersal method, traveling tens of kilometers before finding or establishing a new warren. If food has been particularly abundant and the local population skyrockets, some may cross bodies of water purely in search of new lands on the other side. A few of these half-kilogram adventurers thus made their way across the Accordion Reliquary around 25,000 years ago, island-hopping until they found a new continent, which they now populate in their billions. They have a strange relationship with barrelbanks, which nest closer to water but feed almost exclusively on land. During the peak of summer, the two compete directly, and the smaller whiskerwigs tend to overwhelm the barrelbanks with their higher rate of reproduction. This stifles what would otherwise be a mid-season population boom for the Muridiungulates. But while the Abelitheres begin looking to the streams and ponds for food in the fall, their bigger and stronger hoofed relatives can turn to lower-quality land grasses. When the growing season ends, few whiskerwigs survive to begin breeding again in the spring, while barrelbanks see a low mortality rate thanks to their food reserves, then enter spring ready to start their next generation while the whiskerwigs are still recovering.
The Rooters
This category includes all of the jadeplain's other major herbivores. Some may dabble in grazing or even omnivory, but the core of their diet consists of buried plant matter, including tubers, rhizomes, nitrogen-fixing root nodules, and even the thin, fibrous root networks of jade skystalks. Some live underground in the thin stratum above the water table, while others access roots from above, greatly disturbing the soil in the process. Only one reaches a population density comparable to that of the major grazers like oxen, beests, and apteroos.
The Elastic Groundgoose (Disjunctognathus triplorostris) is the first of the burrowing kiwi family to evolve a truly unique cranial anatomy, and it is already taking the open lands of Ailuropia by storm. Only 300,000 years ago, its lower jaw began to unfuse at the tip, with bone being replaced by stretchy cartilage. The keratinous bill retreated from the jaw-tip, splitting into two parallel rhamphothecae. So far, the necessary musculature has not yet evolved to allow the two sides of the jaw to move up and down independently, but they can pull apart from one another, spreading into a wide scoop that allows the groundgoose to move a third its body weight in soil with each mouthfull. This means it can burrow at an incredible rate of a quarter kilometer per day, spending all its waking hours pushing forward through the soft, loose soil. The tunnel is usually allowed to collapse immediately behind the groundgoose, who has no interest in retracing its path. Navigating with magnetism, it can stay on a straight-line course for many weeks in search of food or a mate, or to escape local predation pressure.
As a descendant of the prairie popbird, this groundgoose was once a highly social animal, relying on the vigilance of its family group to detect predators when foraging aboveground. Now, having become solitary as a result of its newly-turbocharged digging ability, it can no longer risk spending much time on the surface. It may occasionally venture out to clean itself of dirt and parasites, or simply for its mental health; having so recently evolved from surface-loving ancestors, it is prone to getting depressed if it stays in the dark for too long. Similarly, it still has residual social instincts that drive it to seek out others of its species, even outside of mating. These friendships aren't long-lived, as this species no longer builds communal spaces that would facilitate permanent bonds. From time to time, though, several elastic groundgeese will tunnel parellel to each other, chirping back and forth through the dirt until they find reason to diverge.
The upper bill of the elastic groundgoose is strongly hooked, allowing it to tear through fibrous roots and pierce the hard exteriors of bulbs, rhizomes, and root nodules. The bird simply eats as it tunnels, never slowing down, using its tongue to separate edible matter from soil and rocks. Only when it comes time to mate will this species stop moving, and even then, only for a quick twelve-day incubation period. A temporary hub is established, a simplified version of the long-term brooding chambers built by earlier species. The parents dig short tunnels in every direction in search of food, demolishing the root system of a baseball-diamond-sized patch of grassland. The resulting aboveground die-off is a telltale sign that predators are quick to notice; they soon start digging around the area and terrorizing the birds. Luckily, with two doting parents, the chick becomes independent within another ten days, at which point all three groundgeese go their separate ways, unlikely ever to meet again.
The largest and least abundant of the jadeplain's digging herbivores is a member of the graspbird tribe, the only branch of the raspbird family that's currently finding success in continental ecosystems. Close descendants of the mid-Arthrocene graspbird dispersed and adapted across most Panapterran ecosystems around 12,000,000 MPA, long before the breakup of Ailox. Those that made it to Ailuropia became the founders of an endemic genus, sister to all other modern graspbirds. Smaller and more cursorial than other graspbirds, the Burrowing Graspbirds (Terralinguornis) comprise eight species all around the continent. The hallux is lost in this genus, while the other toes have a semi-unguligrade posture. Digit 2 bears most of the bodyweight at the base of the ungule, with the claw itself providing little support. Digit 3 barely touches the ground at the tip of its claw, helping with stability and also carrying about a quarter of the bird's weight. Digit 4's claw is the largest and flattest of all, roughly the size and shape of a small garden trowel.
As the largest member of its genus, the Jade Graspbird (T. longipluma) is around the average size for graspbirds on the whole, reaching just past half a ton. It eats as much as forty kilos of grass a day, but it doesn't just eat the aboveground parts. It uses its beak to uproot a short section of underground rhizome and, using its tongue tines, lifts large sections of turf out of the ground at once. Since prairie grasses often keep most of their biomass belowground, this herbivore has access to far more calories than it could get as a pure grazer, allowing it to become the largest animal in its habitat. Of course, some plants keep their energy reserves further from the surface, and this is where the jade graspbird's massive burrowing claws come in handy. They can excavate around a cubic meter of loose soil an hour, unearthing large tubers that reside three or more meters down. These belong to Giant Jadestalk (Titanoclarisaccharus ailuropiensis), the largest skystalk to evolve since the extinction of pillar skystalks during the Ice Age.
At five meters tall and quite wispy in appearance, a mature giant jadestalk isn't built to last. This terminal growth phase lasts only a few weeks at the end of summer, crowned with a bud that soon matures into a head of over fifty thousand florets, adding two more meters to the plant's height. More flowers may continue growing into the autumn, fueled by vast reserves of carbohydrate energy underground. The long taproot bears a chain of tubers extending nearly as far down as the stalk is tall, and with each flush of nectar and pollen, the plant gets closer to exhausting its supply. In most cases, though, giant jadestalks are brought down by thunderstorms before they run out of energy, leaving stems and flowers strewn across the ground, usually to be eaten by grazers before the graspbird emerges from its shelter. But it knows that a second bounty still rests in the earth, and it uncovers more than enough to satisfy its own appetite. It leaves behind pits and mounds of churned soil, with scattered tubers waiting to be eaten by other species that normally couldn't reach them. At the same time, thousands of small arthropods and burrowing rodents are sent scattering, pursued by little predators that often bide their time around graspbirds...
The Hunters
Apterra's old cast of perching birds has been on the decline for a while now, with downlings in particular seeing a downturn across all three main continents. But the sister clade of the downlings isn't doing too well either. With the rise of perching pouchwings like the stashers, small aboveground predators like the skeeter-snappers are finding themselves outmatched. Both in terms of reproductive output and general movement ability, the older clade is at a disadvantage. But one species has persisted on the jadeplain by becoming more ground-based, at least when it comes to foraging. The 20-gram Rattlesnapper (Crepundiornis parvus) searches primarily for insects and isopods, as it is too small to reliably kill vertebrates outside of a few specific situations. Its beak is shorter than previous members of its family, ends in a sharp hook, and bears a tomial tooth just behind. This allows it to crunch and cut through chitin in a single motion, while still remaining gracile enough to swipe through the air with high speed and precision. This is the skeeter-snappers' only remaining advantage over the more generalized stashers, who can only lash out with their long necks (a more sluggish motion) to catch small and fast-moving prey.
Predation on rattlesnappers comes from many sources; this is the cost of being one of the smallest carnivores around. Though the Crowned Stasher (Ophiothylacavis coronatus) would normally eat the same ground-dwelling arthropods that compose the rattlesnapper's diet, it outweighs the smaller bird by a factor of five, so it sometimes chooses to take out its competition directly. Luckily, the rattlesnapper can repopulate quicker than nearly any other non-clutchbid kiwi. Rattlesnappers nest in the axils of several large jadestalk species, usually around three meters high. The single egg takes around two weeks to hatch, and while the chick is initially altricial, it is independent within another week, allowing its parents to raise another baby every month or so during the growing season. At two months of age, the chick will be having chicks of its own. It will have to protect them on occasion from far bigger predators, and it prefers to deter nest-raiders using its namesake rattling call, which resembles the sound made by stalks of tall grass being shaken by a huge animal. This doesn't always fool the enemy, and the rattlesnapper isn't above resorting to a brawl against a larger foe. Its raptorial bill can tear off chunks of meat from the face of an attacker, and it is made of bone so thin and flexible that it can twist almost 90 degrees without snapping, allowing it to maintain its hold against any attempt to pry it loose. If nothing else, the continued rattling often drives away the would-be thief out of fear that even larger predators might be drawn to the area.
Ratweasels have little diversity in Ailuropia compared to their presence on the other former Panapterran continents. Aside from a handful of small insectivores closely resembling their scurmint ancestor that survived the Ice Age, only one group stands out. Bishears (Duplitondendens), like all ratweasels, have self-sharpening predatory incisors that kill with a shearing movement. However, the incisors of this genus have moved onto the sides of the mouth, leaving a gap at the front. This means, instead of a single forward-directed killing bite, bishears can inflict sideways shearing bites, drawing blood gradually to wear down prey larger than themselves. For the five-kilogram Prairie Bishear (D. brevicauda), this can include targets as large as full-grown battering oxen, which require a pack of raweasels numbering in the double digits to bring down. Their communication skills are better than those of pack-hunting ratweasels of ages past; they rely on an instinctual sign language based on the positioning of white fur tufts on their ears, noses, and tails. From a distance, the most dominant pack member can signal "wait" by holding its tail fanned out horizontally, slicking back its ears, and pointing its nose slightly up. It then turns its head to motion each of its comrades, one by one, into their proper positions for an ambush. Still keeping a nose-up posture, it moves into a vantage point where it can judge the proper timing for everyone to launch their attacks simultaneously. The moment the leader drops its nose and tail, the other bishears lunge, slicing into their prey while it struggles to flee. It may run a short distance before blood loss begins to weaken it, and only then do the ratweasels attempt to grapple it to the ground. The coordination of their group begins to break down as it becomes hard to keep track of one another in the frenzy. Each tries its best not to accidentally land a bite on one of its conspecifics. When the hunt is over, they eat their fill in order of social dominance, then carry any scraps back to the nest for the young and sick. Like most bishears, this species is not completely carnivorous, and it also eats high-quality sweetstalk vegetation, flowers, and soft basket-grass roots. In some of Ailuropia's temperate mountain forests, hundred-kilogram bishears can be found with an almost completely herbivorous diet, but on the jadeplain, the only giant bishear is an obligate meat-eater.
The Dire Bishear (Duplitondendens falxiformis) has reverted to a more typical ratweasel diet of more than 95% animal matter. It too typically starts a hunt with an ambush, aiming to inflict a few deep cuts. It then backs off and allows its prey to retreat, follows it, and launches another assault once it stops, wearing it down until it collapses from blood loss as it tries to run again. Reaching seventy kilograms in its largest males, this species can take down every other animal on the jadeplain save for a fully-grown graspbird. It has greater endurance than its smaller cousin, a necessity as it doesn't live in packs. Two individuals, be they a mated pair, a parent and child, or a duo of siblings, seems to be the limit for long-term dire bishear associations on the jadeplain. They're socially capable of more complex groups, but the prey supply limits the number of top predators can live in one area. And like all bishears, dire bishears are largely sedentary, maintaining a permanent territory where no other individuals are tolerated. A few tens of square kilometers is typical, and while megafaunal prey may be seasonally abundant, any given patch of the jadeplain will see at least a few months a year with very limited game. This imposes the upper limit on settled dire bishear populations, while young wanderers are freer to form larger social networks. Mortality is high at this adolescent stage, for a different apex predator has specialized for following the herds, and it is not predisposed to kindness towards its inexperienced bishear competition.
Carnivorns have a long history on Ailuropia, as this continent birthed the entire clutchbird family. In addition to a few species in the east that have crossed back from Loxodia, Ailuropia boasts an endemic species of macrocarnivorn closely related to the packslash. Macrocarnivornis reverberator, also known as the Trumpeter Carnivorn, weighs a little over 100 kilograms, larger than a single dire bishear, but not nearly a match for a pair working together. Trumpeters don't develop cultural ecotypes as intricate as those of packslashes, and their diets are less varied, as they feed exclusively on a few species of migratory prey all across Ailuropia. They are bigger and stronger, though, and they can communicate over greater distances with their hollow crests. The bony passage of each nostril arcs above the face, creating a pair of narrow resonating chambers. Packs of 20 or more can thus keep in touch across the plains as they track the herds. This increases hunting success by allowing smaller groups to break off and, without losing auditory contact with their packmates, lead a false charge against herds of Muridiungulates, apteroos, or struttios. The herding animals flee right into the jaws and claws of the larger hunting party, who can take down a dozen individuals in a well-planned secondary ambush. Long-distance communication also becomes important during the breeding season, when monogamous couples take turns hunting and sitting on the nest, calling for each other across dozens of kilometers each night. In summer, when the chicks are ready to leave the nest, their parents must teach them how to be a useful member of the team, while also protecting their three-kilogram fledgelings from bachelor packs of fifty-kilogram subadult dire bishears. Mortality may be high for the ratweasels in this coming-of-age season, but the death rate is even higher for carnivorn chicks, less than a third of which make it out of their first summer.
The Exception
One bird genus has pushed generalism to further extremes than any other on Apterra. Prophetornis, the portent pouchwings, are small or mid-sized gamebirds that first evolved in southern Ailuropia and spread slowly throughout the continent, displacing downlings and other small vertebrates as they went. They exploded into Loxodia and Abeli just before the breakup of Ailox, and then spent nearly two million years isolated on either side of the waterway. They caused even greater havoc on the other side of the Reliquary, as they quickly invaded ecosystems that hadn't had time to adapt to their presence. Ailuropia faced a far lower extinction rate, as its fauna had evolved with the ancestors of portents. But a new species was near to crossing back into Ailuropia, one that was no longer so familiar to the inhabitants of its old home. It was bigger, more omnivorous, more aggressive, and had clearly been shaped by the pressures of Apterra's largest remaining interconnected landmass. Its bulk would almost seem overkill compared to the small, less ecologically dominant portents that remained in Ailuropia. When it crossed back to the western continent, would it outcompete its smaller, more mild-mannered congenerics?
No. It had become so different from them that, though its dietary niche remained similar, it didn't greatly suppress their numbers. The larger and smaller portents partitioned their niche not by diet but by life history. The small portents laid small clutches but could achieve two or three generations a year, while this new arrival reared a single clutch of at least twenty eggs just once a year, and took a full year before it could have offspring of its own. It thus followed a longer timescale of booms and busts, but crucially, it remained capable of rapidly increasing its population like any other portent. Though it had less frequent opportunities to do so, it was able to take over the continent in pulses, during which its population increased three or fourfold, before stagnating for many years. It became still larger and longer-lived, increasing the odds that any particular adult would survive long enough to see at lease one bumper year. This required an unusually productive spring, a population crash of smaller portents (most commonly due to disease), and an ongoing population boom of at least one other major prey species. With abundant resources, little direct competition, and a supply of food to distract predators from feeding on their own chicks, a single giant portent could lay two or three tiny eggs a day until it had a clutch of dozens, then raise them in relative safety, ensuring the majority made it through their first year. The bigger the parents, the more eggs they could incubate in their pouches, so, over the course of less than 100,000 years after their return, these already oversized portents have ballooned to an average mass of fifty kilograms.
The modern Omniportent (Prophetornis gigas) is, despite its newfound megafaunal status, still a boom-and-bust gamebird. Adults are not the largest or most well-armed prey on the jadeplain, but those that reach full size can reliably live into their early teens, becoming sexually mature at age two. The omniportent eats nearly any plant and animal matter it can get, from turfgrasses to tubers to large invertebrates, and it will opportunistically scavenge or kill small vertebrates for meat. Every year, omniportent couples incubate as many as fifty eggs in a clutch. Unlike birds that build nests, pouchwing clutches hatch asynchronously, as the first-laid egg begins to incubate immediately. Using hormonal signals, chicks can slow or accelerate their development to compensate. Even still, a clutch laid over the course of two weeks will hatch over the course of four or five days. This slight difference leads to bullying of the younger chicks by their siblings, and in most years, the first few hatchlings will survive, while the rest will starve due to being outcompeted. However, if a predator manages to kill all of the firstborn chicks in the critical first 48 hours after they hatch and emerge from the pouch, their still-unhatched siblings can later hatch and grow freely. More than 95% of chicks won't make it to become independent from their parents at the end of summer, taken by predators or hunger, so it pays to have a backup to prevent an entire breeding season from going to waste.
Perhaps once every two decades, high productivity and low predator pressure coincide to allow omniportents to take over. While most breeding seasons are considered a success if more than one or two chicks in a clutch survive to their first birthday, during these rare events it's possible for an entire clutch to survive and thrive. In a few months, P. gigas increases it its continent-wide population from less than one million up to five, ten, or even twenty million. The overproduction of food is never permanent, and predators eventually exhaust easy supplies of other prey. The bust is quick and unforgiving; most of the new omniportents die a little less than a year after they are born, living on their own in the famine. Older, more experienced individuals go hungry too because of heightened competition, but some survive by turning to hidden food sources, like tubers exposed by jade graspbirds. Two years after the boom, and the omniportent population may still be above five million. A few hundred thousand represent older generations. The overwhelming majority are newly breeding-age adults, with almost zero individuals from the years immediately before and after. Millions of females rear clutches for the first time, most finding no success at all. Millions of males are unable to compete against a much smaller number of more mature and dominant males. Years continue marching on with few, if any, new omniportents surviving childhood. The older generations begin dying out, leaving a population consitituted more than 90% by a single age cohort. Dominance hierarchies weaken; nearly all the males are the same age now. The population declines after five years to just over a million, where it can finally stabilize as chicks begin to routinely survive and recruit into adult flocks.
The omniportent is the first example of a life-history trend that will soon sweep across continents. Apterra's terrestrial megafauna currently comprises mammals and birds that have relatively few offspring at a time. Some Muridiungulates can give birth to ten calves in a litter, and struttios are known to lay a similar number of eggs, while all non-clutchbird kiwis lay only a single egg at a time. Megafauna capable of bearing more than a dozen young per year are few and far between. These slow-reproducing giants tend to have a relatively smooth population pyramid, evenly distributed between individuals of all ages. The omniportent, with its average clutch of four dozen, can suddenly change the structure of its population for many years to come. This creates a ripple effect in its ecosystem whenever this cohort reaches a milestone in its life cycle. When they leave the care of their parents, predators suddenly gain access to unlimited easy prey. As they grow, small predators are forced to look back to their typical prey, which may have undergone a population boom of their own without predators, or may have crashed as food became scarce. When they reach maturity and try to breed for the first time, huge stretches of land are trampled by the flocks in their weeks of energetic courtship.
In the coming ages, more species of birds will evolve to bear such enormous clutches. Some of them will be even larger, even longer-lived, and capable of supporting multiple dominant cohorts at different stages of life. Predator and prey alike will follow this paradigm. Meanwhile, smaller animals will have to play along with ecological forces changing on timescales longer than their own lives.