Fluttering Flickbill

A little brown bird with a wicked beak, the fluttering flickbill lies at the start of a new radiation of diversity of skewers in the early hothouse.

The flickbill is a small, arboreal butterbird descended from the skewer, which is notable for its specialized beak. This bird has now developed the most extreme cranial kinesis of any tetrapod. The cartilaginous joint in their upper bill has elongated to produce two separate points of movement, allowing extraordinary flexion both at the base of the beak near the nares (nostrils) and halfway down its length, letting the beak fold up like the claw of a praying mantis, and to be flicked forward to spear prey. They most often are seen climbing up the trunks of dancing trees, which form the first forests of the hothouse age in Serina's southern hemisphere, and probe for grubs and bark-crawling insects that they can skewer in their bills and fold back toward the mouth. The tongue is lined with sharp hooks and is highly maneuverable, prying the prey off the beak in small pieces and pulling it into the mouth. Flickbills are excellent climbers but weak flyers with a characteristic rising and falling flight pattern, and tire easily, though can sometimes cross seaways if carried by storms or by island hopping between patches of suitable habitat, and so are found in both hemispheres. They most often only flutter from one tree to another, a distance of a few tens to hundreds of feet. Mostly nocturnal, they will emerge to feed a short time before sunup as well as on overcast days, spending the mid part of the day in a secluded tree hole or a thicket of vegetation high in the crown of a tree where their mottled coloration hides them from predators. Occasionally flickbills will feed on the ground in more open habitats with less tree cover; this is more common in populations that exist in the northern hemisphere, where forest is rare. Here the birds are strongly associated with steep riverbanks, glacial erratic boulders, and other elevated land formations where they can climb along a similar vertical surface and find food.

Flickbills, as metamorphic birds, still produce larval offspring, but the diet of this life stage has changed with the adult's new lifestyle. The sap from roots no longer suffices; flickbill babies are mostly carnivorous (though they can also consume fruit) and their parents provide parental care in a remarkably complex way compared to earlier butterbirds, by rearing their young in tree holes (replaced by holes dug into riverbanks in their northern range.) The female's eggs are adhesive and resemble those of amphibians, and are laid in a string along the floor of the nest. They hatch in just a few days, by which time the parents have provided them with prey in the form of a larder of pre-killed insects to begin feeding on, very much like the distant ancestors of all metamorphs did for their young. The young hatch out scarcely a centimeter in length and with little more than biting jaws and the tiniest vestiges of limb nubs, but grow rapidly in the nest that stays warm and humid in the tropical climate. They feed at first by vomiting a digestive fluid onto their food to soften it, later being able to tear pieces of meat with their jaws alone.  Females lay a smaller number of eggs in a single nest, but both parents aid in provisioning it with food and defending it from predators, so that in around two months, more individuals survive to pupate and fledge as fully independent, miniature versions of the adults than they would without this care. 

While young juveniles (which are fully self-feeding and leave their parents) are strictly insect-eating and are stronger flyers than their elders to hawk airborne bugs, adults are opportunistic and slightly omnivorous. They are sometimes predators of other bird's nestlings and eggs, snatching them from untended sparrowgull nests, and may even actively hunt small molodonts in this way. They will also pick very ripe fruit, which may sometimes be fed to their larvae too, though this makes up only a very small percentage of the total diet for either. Though this is only occasionally offered, for adults don't specifically seek it out, flickbill larvae are still similar to their ancestors in that they can survive on a diet of primarily plant sugars, though at a slower rate of growth than on a meat diet.