Butcherbeak

A large metamorph bird with a gruesome face, the butcherbeak has evolved one of the most complex beaks of any bird, living or dead.

Butcherbeaks are large skewers, the descendants of the flickbills that have adapted to catch prey on the ground over the open plains of the early hothouse. These goose-sized birds of the upland plain now have elongated legs and are fast runners, only taking flight when pressed by predators and then rarely for more than a few hundred feet. Their trajectory from a flying, hawking predator to a terrestrial stalker has been swift enough that instead of totally losing their backwards-facing hallux it simply rose up the limb as the bones of the foot grew longer, and because of that it now has little use. Their innermost toe, once able to flex forward or back as needed to climb trees, now sits permanently forward.

The bill of the butcherbeak is still used to catch prey, which has increased in size along with the predator. Adults are now too big to hunt insects; their mandible is now used to stab small molodonts and littler birds with a rapid stabbing, downward strike. The end of the upper mandible is sharply barbed so that this prey becomes skewered and cannot easily fall off, even in flight, letting it carry its prize. The butcherbeak's hooked tongue has increased in size and strength; lined with sharp keratin blades, it fills a similar role to the lower jaw which was lost in their ancestors' evolution, and the skin of the tongue is hardened, with a bony core and sharp keratin spines across its surface. Once prey is hooked in place the beak folds down and its tongue, like the radula of a snail, slices and scrapes the prey animal into small pieces, dismembering it for swallowing, even being able to rotate the carcass as if on a spit to strip it evenly on all sides until only bones remain, which the hunter discards on the ground. When at rest the tongue's spikes are retracted and the whole structure slots neatly into the upper jaw, which may be held out forward like a lance when not feeding, obscuring its complex jointed structure at a glance. Butcherbeaks are primarily nocturnal, with eyes that narrow to vertical slits in daylight but provide excellent acuity in the dark.

As butcherbeaks don't live in trees or even in forested areas any longer, they must put more work to make nests to rear their larvae than smaller ancestors. Females make their own brood chambers, earthen nests up to four feet tall from hardened mud on top of grassland boulders or even directly on the ground. These hollow structures resemble termite nests and have an entrance only a few inches across, too small for the adult to access even to lay eggs within, but this is by design. The female lays her small, adhesive eggs, resembling small clusters of frogspawn, directly on top of small animal carcasses and then drops these into the nest where they are sheltered from rain so that they do not rapidly decompose. Over the next two months she and her mate will guard the nest against intruders and deposit new food as the larvae, which develop first inside the carcasses and then crawl around freely in the nest, become bigger and consume all of their first nursery. The larvae feed first by drinking the fluid from the carcass, vomiting stomach acid to help dissolve the tissue, but as they grow begin to eat similarly to the adult by slicing meat into small solid pieces from the carcass with their tongues. They are blind and featherless and resemble the grubs of earlier butterbirds but are much bigger, up to 8 ounces and 5 inches long, looking like some cross between a mole and a grub with a lone spear-like upper bill and no lower jaw. After a little more than two months they spin a silken cocoon and begin the process of pupation, emerging as a small, fully-developed bird at 80-90 days of age, which leaves the nursery chamber and flies off into the world, fully able to care for itself. These juveniles have longer, more pointed wings than the adults and feed mainly on insects; the developmental transition toward hunting on the ground occurs over two years, at which time the bird is functionally adult and becomes sexually mature.

While male butcherbeaks don't build nests, they aid the female in protecting them and in feeding the young. Their bills are usually as much as 30% longer than those of the female as a result of sexual selection; males prove their competence to partners by bringing offerings of food to potential mates, carefully spearing as many small animals as he can fit on the mandible and presenting them to a partner skewered like a kebob. The more food he can hold at once, the more apt she is to be enchanted by his gift and accept him as a mate.