The Nest Goblin

The Weird Uncle

Tribbetheres are experiencing great success at the start of the Ultimocene. Large terrestrial forms such as circuagodonts have outcompeted many birds on land while tribbats compete with them in the air. One especially strange group of tribbet which is just outside the tribbethere crown group, though, does not merely displace or hunt Serina's birds. It relies on their own instincts to exploit them for its own gain.

The Nest Goblin

It is late spring, nearing Summer in the temperature forests of Serinarcta. Many species of the passerine-like sparrowgulls, a clade of neo-perching birds derived from an earlier radiation of seabird canaries, have spent the past few months incubating eggs and raising chicks, and now many of those young birds have begun testing their wings and leaving the nest. Across a verdant woodland, newly green and in full glory as the warm season approaches its pinnacle, scraggly, clumsy young birds flutter from their nests to low branches. They chirp and squeak, flicking their wings and opening their mouths to reveal the wide red gapes and soft colorful skin flanges on their lips that signal to their parents to feed them. Most species still around now are insectivores, and adult birds, resembling jays and magpies, flit tirelessly from one chick to the next without rest, stuffing gullets with worms and crickets and the bug-like larvae of much stranger avian species.

Some chicks, through lack of skill, tumble to the ground in their maiden voyage. Most typically hop around and find a perch to flap up to quickly, but as soon as this occurs, something strange happens. Hearing the calls of the hungry chicks as they leave their nests, a strange, awkward-looking creature's face peers out of a hole at the base of a tree. Wide, glassy eyes stare out blankly, as a creature who seems to show none of the high cognitive ability of other tribbetheres emerges from a long slumber for its first meal in half a year or longer. It is lanky, totally hairless, with grotesquely large ears and a pointed snout. Long pointed fingers, crusted in the dirt they dug into last autumn, point outward on arms that are still not fully erect. As others emerge from their long hibernation under the forest soil, they resemble the most uncomfortable fusion of an ancient tribbethere ancestor otherwise long gone from this world, the hopper, from which all tribbetheres arose in the late Thermocene - and something very much from a nightmare. They are nest goblins - the most primitive representatives on the line that led to the tribbetheres, a species intermediate between them and the reptile-grade ectothermic tribtiles.

And the calls of the bird chicks make them very, very excited for their first meal in many months.

The goblins are attracted by the calls of the fledgeling sparrowgulls as they leave their nests. They emerge from the dirt like zombies brought to life, pushing the soil away with their spade-like hand, and scurry over the earth like large toads toward the hapless nestlings. The chicks, young and naive, don't run, as the goblins open up their long narrow mouths to reveal shockingly wide gapes lined with small needle-like teeth... and begin, with flawless vocal mimicry, to imitate the baby bird's plaintive peeping, but several times louder, so that it drowns out the birds' own voices in the hum of the forest.

It does not go unnoticed by the parent birds, frantically trying to keep watch of their own chicks as they scatter to the winds around the nest. Hearing the nest goblin's unmistakable cries of hunger, they respond. In the shadow of the forest floor, they see only a crying, red mouth and do as instinct tells them; to stuff it with food. The adult bird lands on the ground next to the goblin, ignoring its own chicks elsewhere in the forest, and feeds it as if it were it own young. Because, as far as it can tell, it must be - the identically imitated voice of its young, uniquely recognizable, is a cue that evolution has endowed this parent bird to recognize.

As it is fed, the goblin hastily gobbles down its fare, but unlike the real chick, it is never satiated. It continues to scream for food, getting only more loud the more it is fed, so that the parent bird works constantly to provide ever more for this nightmarish replacement of its own young, which soon grows from lanky to plump. Eventually, within weeks, the parent bird's own young have either starved or managed to learn to feed on their own and the adult's instincts tell it to move on; but the nest goblin is only just starting its season of plenty.

The goblin, despite its initial seeming lack of intellect, is a master manipulator and a social learner. Not all birds are easily fooled by a generic red gape and an imitated cry; other visual and behavioral cues are required, which the goblin must learn. If a parent bird is unconvinced by its generic, instinctive ploy, the goblin will retreat to the sidelines and observe the bird very closely as it feeds its own offspring. It registers the subtle behavioral cues of the chick, such as the way it may hold its wings or position its head. It listens close, to learn its voice. And with its excellent eyesight, it takes close note of its coloration. And when the adult returns again with food, it is ready. It jumps from the undergrowth, mouth agape, having adjusted the pigment in its skin to such a degree that it now reflects the exact mouth markings of the parents' own chick; traits which evolve in many birds to easily distinguish species from one another - but evolution cannot adapt in a single day to an alien exploiting an ancient system. Not only does it emulate the mouth patterns, but the feather patterns, though to a lesser degree; it copies patterns of light and dark onto its own skin. And for species which flick their wings when begging for food as many do, it precisely does so too - using its enormous ears to approximate wings. Though to us, the bizarre, big-eared goblin - an animal that resembles a toad mixed with a bat - does not come close to resembling a bird chick, the goblin's trick covers every base from which a parent bird identifies its offspring; sound, sight, and behavior. Even the most particular sparrowgull parent cannot resist the super-stimulus of the nest goblin now.

Nest goblins, in just the few months of the year while bird chicks are fledging their nests, gain all the calories they will require for the entire year. While many bird chicks starve, the goblins that have stolen all of their parents' time and attention become morbidly obese. Fed around the clock for weeks without having to move, they swell with so much stored fat that they can barely walk. When the birds finish breeding and begin to molt, losing their seasonal hormones and becoming apathetic to the begging of chicks, the goblins eventually give up. As summer turns to fall and the birds move on, the nest goblins turn their attentions to each other and mate.

They then return to the earth. They dig holes around themselves in sheltered places with their forearms, digging in backwards like frogs until they can cover themselves with dirt and leaves. So hidden, they slow their metabolisms drastically; a body temperature already just on the verge of endothermy and prone to fluctuation drops to ambient temperature. The goblin goes into a deep torpor, and as the winter cold arrives, it freezes nearly solid - only antifreeze properties in its blood prevents its cells from bursting and killing it from the inside out. For up to nine months, it does not move. It shrinks, using its stored fat to survive, so that when the calls of the birds the next spring finally do wake it, it has again become gaunt. Females - which tend to accumulate even more fat than males - will have gestated an embryo all through their dormancy and give birth to a single enormous pup, about 50% of its parents size, upon waking, which is an independent trickster from birth.

With such an easy source of food and a life free of stress, able to effectively shut itself off for most of the year, the nest goblin potentially can survive for a very long time - up to fifty years. Thanks to a combination of novel behavioral and physical adaptation, this last aberrant hopper has found a place, for now, to survive a changing world.

Nest goblins likely evolved from frog-like ambush predators. Adapted to move little and put on much weight by catching small animals that came by, they likely once ate bird chicks. Over time, however, some may have adapted a colorful mouth that could be opened as a threat display to scare off enemies - adult birds that might attack them. Through coincidence and crossing of behavioral wires, a sufficiently wide red mouth would perhaps trigger a parent bird's instinct to feed its young; provided a free meal, these goblin ancestors would have a new source of calories. Over time, the modern nest goblin seems to have evolved to exploit this resource exclusively, ceasing to hunt anything on its own accord and becoming almost sedentary.

Fun fact: Birds have been documented feeding fish on Earth; cardinals are sometimes tricked by the red gape of hungry goldfish in garden ponds, feeding the fish as if they were their own young!

Photo by Paul Lemmons.

And with this, we wrap up our exploration of the tribbetheres for now.