Buttonbirds and Shieldheads

290 Million Years Post-Establishment

A clade of derived osteopulmas, these birds descend from the zebra tweezle and have become some of the most aberrant of all osteopulman birds by the late hothouse, with an anatomy that is difficult to understand at first glance. Buttonbirds and shieldheads are two closely related groups, the latter nested within the former, which are known for their flattened body shapes and specialization toward clinging tightly to surfaces. The former clade, when discussed in isolation, are characterized by specialized wings that fold over their backs and zip together, locking in place over the body and forming a protective covering. The latter clade have lost this trait, evolving a very large and often complex shaped head crest that serves the same purpose and makes the animal difficult to pry up from its perch. The shared clade of all the species shown here evolved from an herbivorous ancestor that clung to tree bark, chewing a hole into the vascular tissue in order to drink the sap that flows within. Most buttonbirds and all shieldheads remain vegetarian today, though the way they feed differs. Some buttonbirds however have become carnivorous. These are the bloodbuttons, and they include both blood-drinking and flesh-eating species, some of which hunt actively, others which are parasites to large vertebrates like thorngrazers and skuorcs.

1. The bark buttonbird is a primitive looking flightless buttonbird species and may closely resemble the common ancestor of all living species which would have first appeared around 7 million years ago. A slow moving, nocturnal animal, it spends its adult life climbing by its toes on high nightforest tree trunks, feeding on sweet sap from incisions it makes in the bark. Adults are flightless, their wings locked together in a protective cloak over their backs which have several stray plumes along their margins that break up their outline and make them harder to predators to spot. What may appear to be this bird's fuzzy body is actually a hard, flat, bony head crest covered in short, variably colored feathers; it protects the bird's neck, an area not covered by the shield formed by its wings, and further disguises its outline to resemble a tuft of moss or lichen, rather than any sort of animal. If spotted by a predator like a taptracker that may try to overturn it and skewer its softer underside, a buttonbird like this will clamp itself down to the bark, lock its toes in place with specialized tendons, and hold on for dear life. Its rounded shape makes it hard, though not impossible to pry up, and it will shed brittle down feathers that fall apart on contact into irritating dusty shards that can cause pain in the eyes and nose of an attacker. Bark buttonbirds are very common, but solitary and difficult to spot, and have maximum adult lifespans of about 5 months. Females lay comparatively large eggs in the sap channels they pierce into the trees, only in small clusters of three to five at a time, which is very unlike the huge egg clutches of most osteopulmas.

They and all buttonbirds are unique for passing through only a brief larval stage within the egg and emerging as a small, fully-formed juvenile with all the traits of the adult already present to some degree, though one which is still extremely modified and already flattened in shape. In this species, the newborn is around half of a centimeter long and among the smallest of all non-larval birds ever to exist. It is somewhat more mobile than the adult and scurries around - this life stage exists to disperse it away from its parents, preventing inbreeding. It clings to the bark, moving with a sideways crawling motion like a crab, and can dash quickly to escape predators. It does not develop full wing plumage for about ten days, after which it has traveled up to 1000 feet away from where its egg was laid, or occasionally more if it is carried on wind or some larger animal. Then it takes on a more adult appearance and becomes much more sedentary; adults are fully mature by 4 weeks of age and around one inch in total length, and when fully grown may only travel 5-10 inches per day.

2. Mutton buttons are parasites that spend their lives on large animals, especially favoring gantuans like cygnosaurs. They diverged around 5 million years ago. Their choice of habitat is very unlike that of their plant-eating ancestors, but the shift to clinging to animals came only after their ancestral lineage began feeding on other species of bark buttonbirds by flipping them over with large, hooked mandibles to gnaw into their underbellies. Occasionally, button birds of all species can become dislodged from their host trees or disperse accidentally onto passing animals, which for most is a fatal mistake if they cannot find their way back to a tree to feed. But once the mutton button adapted to make use of animal protein as a diet, this was no longer a tragic misstep but an opportunity. By dispersing as juveniles onto animals, they could be transported far from their place of birth before hopping back off to lay their eggs. It was then only a short jump to laying their eggs directly on their hosts, abandoning trees entirely.

Mutton buttons lack the shape-disguising tufts and uneven edges of arboreal buttonbirds, having reverted to a smooth, dome-like rounded wing carapace and a simple, unadorned head crest. They are extremely resilient to crushing, as their wings and crests form a barrier that can endure a tremendous degree of pressure from pest-eating birds or the host animals themselves as they scratch themselves, and they secure themselves to the skin by digging in with their closed beaks and then opening them whilst buried in flesh to prevent their removal. They move very little as adults, traveling about twelve inches only every few weeks after they have carved out a coin-sized depression in the skin of their host up to 1 inch deep; antibacterial enzymes in their saliva keep the wounds from being infected as it continuously chews them open and prevents their healing. Their eggs are laid within these wounds and protected until hatching into juveniles, after which the adult moves away and makes a new feeding site. Mutton buttons and other members of the bloodbutton clade go through two distinct life stages before adulthood, but also lack a larval period. They hatch out in a similar state to the bark button, but do not travel far, feeding in the flesh-tunnel carved out by their mother for around 15 days and extending it up to 4 inches under the skin, hiding them from predators. After that, their first wing plumage has grown in and they can briefly fly; they will travel to another animal, sometimes being carried in the wind for several miles, though they are weak under their own power. Once settled on a new host away from their relatives, they will mature into the sedentary adult form and begin breeding by the age of 5 weeks. Most mutton buttons live around 6 months and reach one inches across. However, if they avoid predators, adults continue to grow slowly throughout life, and the oldest adults may reach three years of age and grow to up to a giant 2.5 inches across, resembling strange barnacles that slowly eat their hosts alive in small enough bites that they remain a nuisance rather than a deadly threat. Though their feeding is gory and likely painful, the antibacterial properties of their saliva can provide benefits to otherwise injured hosts, as the buttons are drawn to open wounds such as from larger predator attacks, and as they feed they will clear out pathogens which could ultimately cause fatal infections to the animal.

3. The baffling boomerang is a shieldhead, a derived group of buttonbirds which has remained an herbivore and traded its wing carapace for a much larger head crest serving the same purpose. Still living in trees, this species of Serinaustra's everdant forest now uses the separated, frayed barbs of its wings as feelers to detect predators approaching and to further break up its shape against the background to hide. Colored in very variable shades of brown, grey and green, the boomerang is named for the shape of its head, which could also be compared to a crescent moon. Rather than mimicking any particular shape, like a leaf or stick, its odd shape seems to exist simply to make its outline hard to identify, so that predators cannot recognize it as food. The "baffling" in its common name refers to its extremely odd shape; when viewed from above, nothing of this bird is visible except its bizarre head crest, the top of its bill, and its eyes.

Boomerangs are herbivores but not sap-feeders. Instead they feed directly on tree bark itself, and have symbiotic gut microbes which can digest cellulose, making this a nutritious and unlimited food supply, which in turn can sometimes let boomerangs reach high populations. They can aggregate in colonies of thousands on trees when conditions are ideal, their crescent shaped heads interlocking together as they end up nearly on top of one another. Individually each one causes negligible damage to a plant as it chews the bark into rounded pits, rotating itself around the pit as it feeds and so making perfect circles in its wake. In swarms, however, thousands of these pits in the bark weaken trees and may cause their deaths. They lay their eggs in these pits, giving their juveniles a softened place to start feeding before they are strong enough to bite into unchewed bark, and also allowing them to acquire the necessary microbes for their digestion which are passed from mother to offspring in the saliva she leaves behind. Boomerangs are a flightless species and the newborns resemble adults but lack their head crests, which take up to 2 months to reach full size. Until then they will hide close to adults for protection, but are still subject to increased predation until that defense has developed. This species only rarely reaches plague populations, even though their food is unlimited, because once they are densely populated on a given tree it becomes easy for predators to spot them, because seeing just one move will reveal a chain of individuals that were hiding close by their neighbors. The crescent shaped head crest makes them hard to swallow whole, but is easily broken by chewing; scarreots are among the most important predators of this odd fellow metamorph bird, for they can pry them off the bark with their mobile beaks and crack them into manageable pieces before consuming.