Flightless and Flesh-Eating

After 5 million years of churning time, two similar-looking birds have sustained the terrestrial predator lifestyle. Though they were once similar, they have diverged much in the intervening years. In the Americas arose the sicklebirds, derived from the seriema, while in Afro-Eurasia-Australia, the similar-looking secretary birds diversified. These two ancestors, seriemas and secretary birds, were strongly convergent despite their distant relation. Seriemas are the last of their order, with no close living relatives, though their extinct kin included majestic carnivorous birds such as the terror birds. Secretary birds, meanwhile, are birds of prey, related to the familiar hawks, eagles, and vultures. Though unrelated, they are both long-legged carnivorous birds, kicking snakes, lizards, small mammals, and other quarry, or beating them against the ground. They both can fly, though preferring to run. Separated by space and time, however, and subject to circumstance and chance, they have left the form that graciously bought them both their survival.

With some attention to detail, these two animals still have some things in common. They both tend to be much larger than their ancestors. They are both flightless, yet retain at least some use of their shrunken wings. Their legs, meanwhile, are relatively much shorter than they were before, adapted to fast, energy-efficient running as opposed to kicking. Finally, they are quite specialized in carnivory, but with their increased size, their hunting and killing tactics are much changed to cope with larger prey.

The similarities end here, however. Most obviously, chancellors are much larger than their American counterparts, having claimed the apex predator spot in much of their range, as their predecessors had even 2 million years after the extinction. Africa fared worse than South America, lacking a north-to-south mountain chain to house would-be survivors, and a restricted flow through Arabia until 2 million years after the extinction allowed chancellors to take the top spot. Meanwhile, South America had more mammalian competitors from the very beginning, largely excluding sicklebirds from the apex role.

Sicklebirds in particular have capitalized on their most defining feature, their sickle-shaped first claws, turning them from an aid in pinning down prey to full-blown main weapons. Instead of picking up and tossing prey or slamming it into the ground, sicklebirds instead pin down their prey before it is even dead, pouncing upon it after running at speed and grabbing tight with their sickle claws. With its claws so embedded, it tears at the animal with its beak, maintaining control on top of the animal by flapping its wings and maneuvering with its tail. For this reason, it maintains fairly large wings and a developed tail, for it is vital for the predator to be atop its prey in the killing struggle. The prey will soon die from stab wounds and bites, but the bird does not need to kill the animal before eating, consuming its flesh as it perishes. It is quite convergent with the long-extinct dromaeosaurs or "raptors".

Chancellor ancestors, meanwhile, lack the unique claw of seriemas, but inherited their derived meat-tearing beak from their bird-of-prey ancestry. As their beaks became more and more important for prey killing, they developed tomial teeth to better manipulate and tear into their quarry. These tooth-like extensions of the beak are a feature that has evolved many times in birds of prey as a whole, such as the double-toothed kite, sharp-shinned hawk, and even in the unrelated falcons. This was their state 2 million years hence, using their beaks as sharp, tearing clamps. However, with ever-rising competition form mammals, many of which crossed Arabia into Africa, the widespread proto-Chancellors were forced to innovate, and innovate they did. Lacking the axe-like killing blows of terror birds, these birds instead targeted weak points on the body, settling for their prey's throats. Once biting throats became habitual, their tomial teeth found a new use, and their fate was sealed. Now, their curiously toothed beak, combined with their ancestral clamping method, is used to snap shut around their prey's throats, crush-cutting the trachea and neck vessels. Their beaks are shaped like domes, effectively transferring force to the prey. This method of killing is called a throat clamp, and is convergent with dogs, cats, and their relatives.

Chancellors' convergent throat-clamping ability holds advantages and disadvantages over the many mammalian predators —  mostly mustelids —  that it shares its habitat with. Quite advantageously, a single chancellor can throat clamp a prey animal with little risk to the predator, standing upon it with a foot while reaching over and clamping the neck. Their necks may be stiff and inflexible for a bird, but they are still limber enough to reach this far. In contrast, a mammalian throat-clamper exposes itself to deadly kicks as it stands directly in front of the animal it is killing. This clamping versatility allows chancellors to nab their prey's throats quickly in a fight, ending it quickly. However, chancellor beaks are more prey-specific than the toothy maws of mammals, requiring that the throat is a particular size to fit properly in the beak. This means that chancellors are less effective versus unusually sized prey throats. Thus, the chancellors tend to be more species-rich, speciating into a rainbow of sizes, while their competition is less so, but more generalist. Though they look dinosaurian, unlike sicklebirds, no dinosaur before has ever used this tactic, making them quite novel.

The specific chancellor species presented is a grand rubious chancellor, a medium-large example. Still, it is huge, weighing over twice as much as a man and able to see straight over his head. Upon its brow is a feature common to many chancellor species: A tuft of stiff feathers to keep the sun out of the eyes. It lives in the southern veldt, between the equator and what would be South Africa, preferring cooler climates. In the winter it toughs out the cold in its heavy feather pelt, preying on vagrants and consuming carrion, while in the summer it chases down large ungulate prey. Their brownish-red coloration is odd, though not unheard of for large predators, and the reddish soils and widespread Themeda triandra grasses help camouflage them.

The sicklebird, meanwhile, is a kou-ka, living in the taigas of South America. It is a giant among sicklebirds, though not among flightless birds in general, for it is just smaller than a southern cassowary. For most of the year, their characteristic "kou-ka!" calls echo through the pine trees; shorter-range vocalizations include growling and low-pitched chattering. When winter comes, they flee into the grasslands up north for a more survivable winter. Adept at chasing prey both in stands of trees and in the open, they make quick work of anything from small lizards to adolescent guanacos. Fallen to this kou-ka is a young badger-hare, all fattened up for winter. These also have a penchant for meat, for they are omnivorous hares that are just as likely to jump away from predators as upon a prey animal. They are more than just sicklebird chow, as will be later explored.