Higher Gilltails

Hothouse gilltails are strange birds even in a world of strange birds. Forms such as the gloomswallow are more primitive, little changed overall from middle-Ultimocene species such as the tufted frogjar. By the late Ultimocene, some gilltails have become more derived and even more unusual. They are the higher gilltails - and they are a taxonomist's nightmare.

Higher gilltails are around 17 million years divergent from other gilltail groups. They are all plain as adults, relative to other metamorph birds, with conservative morphology, bipedal stance, beaks, feathered wings, and no wing digits after metamorphosis. Superficially sparrowgull-like, they can be distinguished externally only by the presence of four-toed feet and less obviously by the patterns in which the wing plumage grows. As larvae, these birds do not stray too far from the "norm" established by their earlier ancestors and extant primitive relatives. Where this group gets very weird is in how extremely they change morphology over the course of their lives, and how rapidly these changes occur in related species. There is no physical way to tell which higher gilltails are related to each other. While all conventionally bird-like, they cover a range of niches and body shapes, and within a genus can look so dissimilar as to appear completely unrelated. There is also no physical way to tell which adult is the same species as a given larvae. Larvae and adults virtually never share a diet, an adaptation that prevents intraspecies competition. This means that carnivore larvae turn into vegetarian adults, and the reverse is true as well. This requires severe restructuring of the skeleton and other anatomy, particularly of the jaws, which must occur during pupation, as an intermediate stage between infancy and adulthood would be deformed and simply unable to survive. Larvae may develop powerful cutting jaws in infancy to fulfill a predatory role, only to shed their entire bill in pupation and grow a new, differently shaped beak to process a diet of leaves as an adult. Alternately, some larvae have adapted to scrape algae from hard surfaces, developing a blunt, rasping bill that is completely transformed by adulthood, growing long and sharp, suited for predation. Because every larval higher gilltail transforms itself so much during pupation, species can change massively from each other in a short time if a mutant individual changes in just a slightly different way, completely reshaping its facial structure or the length of its limbs from just small developmental mutations. No other birds experience such extreme changes to themselves in a single lifetime.

The grazergrouse is a small, dove-sized plant-eating bird native to sogland habitats in northern Serinarcta. Its beak is wide but very blunt, shaped more like that of a tortoise than most birds - well-shaped to crop vegetation down low to the ground. It runs quickly on four-toed feet, and all its toes face forward, an unusual condition among birds, but not one which is too obvious at a distance. Meanwhile, the swampsnapper is a large fish-like animal up to 30 inches long. It moves slowly over the mud at the bottom of slow-moving waterways, waiting for some fish or insect to move just a little too close, then lunging and catching it in a long beak lined with very large hooks. These animals are the same species; they spend the first five to eight years of their lives as the latter before burying themselves in damp air pocket in the riverbank and transforming into the former over the course of around 120 days. The grazergrouse life stage lives around nine months, and can reproduce within days of adulthood - females are pre-equipped with their first clutch of up to 10,000 tiny eggs, each like those of a fish or a frog, which are formed during pupation from energy metabolized as most of the larva's body is absorbed over development into the far smaller adult. Carnivorous swampsnappers drop their beaks during metamorphosis, regrowing smaller, simpler ones to suit an herbivorous adult diet.

The horned dartlark is an opposite example to the life history adapted by the grazergrouse and the swampsnapper. It begins life as an herbivorous larvae, which eats algae from stones in flowing Serinaustran rivers. Its beak is turned slightly downward and is both short and very blunt, shaped to rasp rocks and remove thin films of vegetable food. Large, keratinous spikes grow from either side of its jaw and from its elbows and ankles, anti-predator adaptations that make it hard to swallow whole. This has evolved primary to defend it from its own parent - as an adult, the horned dartlark is a piscivore which hunts fish (and fish-like animals) from the edge of the very same rivers, diving off branches or rocks and pursuing them underwater like a dart. Finding its own young too sharp to consume, it quickly drops them, and so avoids inadvertently feeding on its kin, even though adults have no recognition of their own offspring's very different appearance. These spiny protuberances dissolve during pupation, which occurs below water in a cocoon of fibrous silk covered with small pebbles or wood debris, stuck beneath a large boulder. When the young adult bird emerges, its beak now much longer than before and its body covered in perfectly formed feathers, it swims to the surface and climbs out on the nearest object to dry itself for the first time and preen its feathers. It will be able to fly in just an hour. Unlike the grazergrouse and the swampsnapper, the horned dart lark is much longer lived in its adult stage; a larval period of 9-12 months ends, and the adult then may live for ten or more years, reproducing annually.

Firetuft birds, too, start life as algae-scraping vegetarians, and transform over time into killers. Closer related to the dartlark, their infancy is even more brief, and usually lasts just 6 months. They favor unpredictable habitats - shallow, anoxic pools of water cut off from other flowing rivers or lakes, as may sometimes occur in the soglands of the southern upperglades where large animals have formed mud wallows. In this habitat, they have no competitors, but food may also be scarce. Their primary diet is another eager colonist of harsh and undesirable water bodies, cyanobacteria, which can quickly cover nutrient rich, low-oxygen muddy water in a carpet of green, blue, or red slime. Many of these bacterial mats are toxic; on Earth, when they bloom too abundantly, they poison marine life, and when filtered from the water by shellfish, these animals too can poison humans if they then consume them. This is exactly what the firetuft bird has evolved to do. Immune to concentrations of cyanotoxins fatal to most animals their size, the larvae graze the mats of slime and quickly grow up to 11 inches long. They advertise their toxicity after around 10 days of age with a bright warning pattern of black, red, and yellow, telling other animals to stay away or die. To breathe in these pools when oxygen is scarce, they lift their tails above the water; all of their gills are located in one tuft at the very end, and as long as they stay damp, they can take up oxygen from the air. Firetuft birds transform as quickly as they can, forming cocoons in the mud. When they emerge, some 75 days later, the adult retains the vibrant hues, and remains no less toxic than its larva. Storing the poison in the fat and muscle tissues of its body, it will remain potent for over 2 years without being replenished. The adult is a predator of flying insects and an agile flier, often sitting on a tree branch and then launching itself into the air after a passing bug. Adult firetuft birds can live more than 5 years; the toxicity of older adults lessens and eventually is diminished altogether. Even an old bird continues to wear its warning colors, however, and is still left alone, because by that point, nothing will dare question if it could be lying.