Burdles

Some of the most abundant marine birds which can be found in the warm oceans of the Pangeacene are the entirely aquatic, sea turtle-like descendants of the maritime muck known as burdles. Completely featherless, covered in scaly hide and with mesothermic metabolisms, while some of these strange birds returned to the land full time to give rise to large terrestrial herbivores, by far the more successful group by 228 million years PE, following the success of changelings and tribbetheres in herbivorous niches, is a branch which specialized in the opposite direction, becoming more aquatic and nearly severing their ties to land. Their wings become even more adapted into large paddles, which the bird used to power its movement in the water, while the sprawling hind limbs shortened into steering flippers and moved to the extreme rear of their bodies. These unusual aquatic birds now glide lazily through all of the warm seas across Serina, feeding on a variety of easily-obtained food sources that don't move too quickly to catch, from water plants to jellyfish - diets which can both be found in abundance along Serina's various reef-types and aquatic grasslands, which all support their own endemic varieties of aquatic muck.

above: two jelly-eaters, a group of carnivorous burdle with specializations to feed on jellyfish, feed on their preferred prey. In addition to grazing on the edges of defenseless chainjelly colonies (above), these leisurely hunters also tackle much more formidable stinging prey (below), their throats covered in a defensive armor of keratin spikes that serve both to guide their gelatinous food down the gullet and protect their throats from stings.

Illustration by TrollMans

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Burdles now find all of their food underwater and even drink seawater, ejecting the excess sodium as a caustic spray extruded from specialized glands in their nostrils. Living in the tropics and further insulated by thick layers of muscle and body fat, they can produce enough warmth through their movement that they do not need to haul themselves on land to bask. The only time that a burdle must return to land at all is to lay its eggs, and thus only the female ever does so. Like a sea turtle, she frequently returns to the same beach from which she herself hatched and deposits a clutch of eggs into the sand, which will hatch alone in the world and make a mad scuttling dash to the sea on their bellies, between predators and obstacles, which only a small percentage will likely complete. In order to lay all of her eggs at once to a single trip ashore, she stores them as they are produced in a special pouch branching off her oviducts. Producing three daily, it takes her up to two weeks to lay her full clutch. Her eggs have become soft-shelled so as not to crack as they are stored. The consequence is that the embryos cannot leech as much calcium from their eggshells in development and thus, as in bumblets, the young hatch out with highly cartilaginous skeletons which ossify in the months following hatching.

Most burdles are solitary animals, particularly those which are carnivorous, and are largely indifferent to their kind except to mate. Some grazing species, however, are highly social and move in large herds for protection. Though there is no active parenting in such species, as none would recognize their chicks even if they met, the younger and more vulnerable individuals stay close beside their older peers in an effort to dissuade their predators from approaching. Newly-hatched individuals often gather in swarms underneath the bellies of their elders for protection against seabirds, while yearlings - less vulnerable to airborne threats but still easy pickings for aquatic hunters, ride just on top, to help prevent an ambush from below.