Spec Dinosauria: Twitiaviformes

INRTODUCTION

Some of the differences between Specworld's biota and that of our timeline are shatteringly apparent. Others, like the twitiaviforms, are of a far more subtle nature. The first Specworld explorers, once the novelty of walking with dinosaurs had worn off, were astounded (or disappointed) by the many similarities between the fauna of our two timelines, in particular amongst the birds. Both our worlds possess fowl (Galliformes), penguins, petrels, small herons, waterfowl (Anseriformes), and charadriiform waders. But looks can be deceiving.

During the initial surveys of Specworld's fauna, the "little brown jobs" seen merrily singing in the bushes were assumed to be passerine birds. Similarly, Melanesian birds with huge, curved beaks were written off as "hornbills". More detailed anatomical analyses of these forms flushed these assumptions down the proverbial toilet with a loud, embarrassing gurgle.

BIOLOGY

The startling truth soon became apparent: There are no passerines in Spec.

Unlike our world, where a single bird clade (the songbirds, Passeriformes) exercises near-total dominance over the small-bodied insectivorous and seed-eating guilds, similar niches in Specworld are divided between 2 bird groups (Twitiaviformes and Allospiziformes), neither of which is present on Home-Earth. The former taxon, the tweety-birds, fill habitats around the world with their twittering cacophony.

With few exceptions, tweeties are externally quite unremarkable looking birds. The majority are insectivores, although some eat seeds, fruit and nectar. About half of the twitiaviform species, including all the seed and nectar feeders, have clusters of bristles on their tongues to assist in feeding. The clade has entered niches not occupied by the passerines, including large hornbill and toucan-like forms.

The evolutionary relationships of the tweeties has been one of the most intensely debated subjects on Spec. Before the existence of archaic bird lineages like the Enantiornithes and Xenornithes on Spec was established, it was long assumed that they represented an unusual lineage of Neornithes (the clade to which all living Home-Earth birds belong). It was proposed that they may have been highly derived palaeognaths that had convergently evolved neognath-like features of the palate or perhaps primitive "proto-neognaths" that still retained old-style ankles. The shoulder configuration tended to be overlooked in favour of features of the palate and the hindlimb musculature.

The anatomy of the tweety-birds immediately sets them apart from all other avians, however; tweety skeletons that declare that they are not neornithian birds at all, but rather enantiornithian 'opposite birds' like avisaurs and allospiziforms. Not much more than their shoulder anatomy labels the tweety-birds as enantiorniths, but most scholars place them close to the Allospiziformes, though since these two taxa have been separate since at least the middle Late Cretaceous, 'close' is very much a relative term. Some have even tried to interpret the highly fragmentary Alexornis from the Early Cretaceous of Mexico as the earliest known tweety-bird.

Tweeties have changed much in the last hundred million years, and now closely resemble the passerines on which they have converged. Twitiaviform palatal configuration is unique, with large pterygoids with dual moveable joints to both the palatine and the large basiopterygoid process. The vomers have been reduced though not to the same extent as in the neognaths. This configuration allows for far greater palatial mobility than most other primitive birds but less so than in neognaths, which was probably reason why this clade has produced few finch-like seed-crackers – that niche being filled by the allospiziforms.

Additionally, the ascending process in the ankle originates on the astragalus (as in most other theropods) rather than the calcaneum (as in neognaths). Save for a few insular forms, tweeties are strong fliers with well-developed keeled sterna.

A more remarkable aspect of twitiaviform biology has recently come to light which may hold the key to their success – the majority of twitiaviforms are poisonous for at least part of their life-cycle. In Home-Earth's avifauna, the presence of poison in birds is restricted to a handful of passerines from New Guinea whose feathers and skin are laced batrachotoxins – and even here the toxins are apparently not produced by the bird but rather sequestered from another source.

On Spec, the use of secreted chemical toxins has become a common defence amongst the tweeties. Special glands on the chest secrete a mild haemotoxin that makes the act of biting into a live bird both distasteful and, should the poison make contact with an abrasion in the mouth or gut, very painful. The birds appear to be totally immune to the effects of their secretions, and those which retain this feature in adulthood are often seen laboriously applying over their body with their beaks.

In the majority of species, the toxins are present from about half-way through the incubation period and soon permeate most of the egg. The poison is retained in hatchlings and young birds, providing vital protection during this precarious stage of life. After the bird gets its adult plumage –somewhat later than similarly-sized Home Earth passerines–, the secretions usually stop. In a minority of species, the poison retained in adulthood; these are usually very small, spectacularly coloured rainforest denizens. In others, particularly insular forms, the ability to generate poison has been lost altogether.

Thus most tweety-birds possess a potent defense against any nest-raiding predator that does not possess specific physiological or behavioral adaptations. To a lesser extent, the poison may also provide some protection against parasites. As a result of their toxic offspring, twitiaviform parents generally have a much easier and stress-free life than a comparable brooding passerine couple. They tend to produce small clutches, some species investing in only one or two large eggs per season. As the eggs are usually toxic in the days prior to hatching, less effort is put into concealing and protecting the brood from predators. In fact, the eggs of some twitiavians are the most beautiful in the animal kingdom being adorned with bold, colorful warning patterns (as can be expected, some birds with non-toxic eggs practice egg mimicry). Expectant tweety-parents are often quite lazy when it comes to nest protection, some seem to actively goad potential nest-predators into sampling their distasteful clutch (on the other hand, this behavior tends to open them up to brood parasitism).

The hatchlings are large and become fully mobile within a day or two, capable of hopping amongst the branches or foraging on the ground. They still stay close to the nest for some weeks with the parents bringing food to their young to supplement their diet. The young soon leave the nest to lead their own lives, generally staying out of the way of older birds until having reached sexual maturity, after two or sometimes even three years.

The Twitiaviformes are distributed worldwide with about 2000 living species in 16 large groups. The tweeties are much more diverse in the Australasian and Neotropical regions than in the northern continents; probably the rigors of the ice ages and the lack of natural barriers in the north has led to a poorer degree of speciation.

The oldest definite tweety-birds so far come from Messel. Some seem to be related to wagtail tweety-birds and mistriders, while others resemble scytherbills and sturdybills.

TWITIAVIIDAE (Wagtail tweety-birds)

These archetypical tweety-birds form an almost cosmopolitan clade of small-medium sized ground-dwelling birds with slender bills and legs. They are mainly brown in color although may be boldly marked. The walk has a pronounced swagger that jerks their long tails in a manner similar to our world's passerine wagtails. They run after insects, leaping to pursue them in flight, but also take seeds and vegetable matter.

Black-Faced Tweety-Bird (Twitiavis superciliosus)

Black-faced tweety-bird, Twitiavis superciliosus (Australia and Papua)

The black-faced tweety-bird was the first twitiaviform to be described in detail, which is not surprising as they are absolutely everywhere in the open environments of mainland Australia and southern Papua. Vast, nomadic swarms, accompanied by their chattering twitters, fill the skies of inland Australia (although the birds are just as at home in woodlands and heath near the coast).

Smelly tweety-bird, Fragravis choobenseni, (Australia)

Unexpected tweety-bird, Fragravis inexpectata, (Pauan)

Songs of individual birds are quite melodious but quickly degenerate into earsplitting noise-pollution when competing with hundreds of their comrades. They are quite fearless and will accompany large animals, chasing insects disturbed by their footfalls.Two new species of of tweety-bird were discovered following a recent expedition. Smelly tweety-bird (Fragravis choobenseni) and the Unexpected tweety-bird (Fragravis inexpectata).

ARBOROGEMMIDAE (Treegems and treeclutchers)

The treegems or treeclutchers are small trunk- and branch-foraging twitiaviforms restricted to Australia, Tasmania and Papua. They cling to tree trunks with strong, robust legs and use their long, slightly upcurved bills to lever off bark in search of prey - usually insects, their larvae, and spiders.

Golden Treeclutcher (Yerao aureus)

Tasmanian golden treeclutcher, Yerao aureus splendidus (Tasmania)

Golden Treeclutchers are abundant in the temperate forests and woodlands of Southern Australia. Males develop bright yellow feathers during the breeding season which attain an intense metallic sheen in the Tasmanian subspecies.

PSEUDARTAMIDAE (Mistriders)

The mistriders are distributed worldwide. Their rather dull and non-descript appearance is more than made up for by their breathtaking flying skills – they are the only twitiaviforms that engage in soaring flight. The name "mistrider" was inspired by accounts of these birds in the highlands of Australia and New Guinea, darting in and out of the morning mist.

Though mistriders have well developed brush-tipped tongues and feed upon nectar in certain seasons, the bulk of their diet is made up of aerial insects.

Black-Collared Mistrider (Pseudoartamus collaris)

Black-collared mistriders, Pseudartamus collaris (Australia)

The black-collared mistrider occurs throughout mainland Australia, tending to move south during the spring. This widespread species feeds mainly on aerial insects, but also gleans prey on the ground, and especially the young individuals (up to a year in age) are very fond of nectar

THERIZINORHYNCHIDAE (Scytherbills, channelbills, sturdybills, long-fung, and cacklers)

Therizinorhynchids include the giants of the Australo-Asiatic twitiaviforms with many large and colorful forest forms, although the family also harbors a number of midgets. Their most distinctive feature is their enormous, lightweight bill, superficially similar to those of our world's toucans (which do exist in Spec's South America) and hornbills (which never evolved in Spec).

With a few exceptions, therizinorhynchids are denizens of rainforests and tropical woodlands where they feed mainly on fruit and some small animals. They consume hard fruits by mashing them within their beaks whereupon the pulp is collected with their brush-like tongue. Like hornbills and toucans, they nest in excavated holes in tree-trunks.

The family reaches its greatest diversity in Melanesia, New Guinea and the Philippines. The group is poorly represented in Australia with only 5 species, 2 of which are endemic.

Superb Scytherbill (Scythrhynchus superbus)

Male superb scytherbill, Scythrhynchus superbus (Southern Papua, Aru islands, and eastern Australia)

One of the largest therizinorhynchids, the superb scytherbill is found throughout Southern Papua, the Aru islands and eastern Australia in moist lowland forest habitats. The majority of the Australian birds are migratory, crossing the Torres Strait to winter in New Guinea. Females are similar to the males but have smaller, duller throat-wattles and lack the male's head crest.

Celestial Long-Fung (Phoenix mirabilis)

Celestial long-fung, Phoenix mirabilis (Southeast Asia)

Members of the clade Phoenix are never more than 20 centimeters in length (not including the tail), and possess short, sharply curved bills and long, bristle-tipped tongues with which the lap nectar out of flowers.

The symbiotic work these the long-fung do for their flowers is actually of a rather dubious nature. While the birds do function as pollen-transport for flowers, they have a definite taste for the pollen, itself, nibbling on flower stamens to obtain valuable protein. As a result, may of the flowers of Southeast Asia (even those of totally unrelated species) possess the distinctive "pleated skirt" shape, which allows the birds to extend their beaks into the nectar reservoirs, while the pollen is deposited safely on their heads.

Long-fung are widespread across tropical Asia and Melanesia where vast long-fung flocks blanket trees and blot out the sun when in flight. The celestial long-fung (Phoenix mirabilis, pictured above), is the most common species of mainland Southeast Asia, and possesses the short wings and luxurious tail feathers that characterize the genus.

Cackler (Gracillarus gracillare)

Cackler, Gracillarus gracillare (Southern, southeast, and east Asia)

Cacklers are ubiquitous across Spec's Indochina; their distinctive, laughter-like call rings from almost every treetop. Drably-colored for a scyther, the cackler is an omnivore with definite carnivorous tendencies. While these birds will eat fruit, and juveniles will occasionally drink nectar, the bulk of a cackler's diet is made up of smaller vertebrates, such as lizards, snakes, and mammals.

Cacklers do not flock together as do their cousins, the long-fung, but travel as mated pairs or small families. Like all scythers, cacklers nest in hollow tree-trunks, the female brooding over eggs or newly-hatched chicks, while the male and older siblings forage for food.

Red-Faced Sturdybill (Robustirhynchus rubicundis)

Red-faced sturdybill, Robustirhynchus rubicundis (Southern Papua, northeastern Australia)

These birds habitually make their homes in the large, tower-like nest of the architect ant, a common insect across Australasia. Normally, these ants are fiercely protective of their nests, ripping any intruder apart with powerful mandibles. The sturdybills, however, may come and go from the nest's upper chambers completely unmolested.

Analysis of the sturdybills' twitiaviform secretions (which the birds produce throughout their life) has proven that the toxins mimic the pheromone signals of the ants, making their secretors "invisible" to the insect colony. The sturdybills, in return for the scraps of fruit and leaves they pile within the nest, receive the protection of a virtually impenetrable fortress. The relationship between these two species, therefore, is rather one-sided, with the birds receiving most of the benefits, but the ants do not seem perturbed by their giant neighbors.

BALACLAVIDAE (Balaclavas, masques, glitterbirds, skoshis, and jimentori)

This huge group includes some of the most bizarre and beautiful members of the clade. Many members of this group possess a wrinkled sheath of thick leathery skin that covers up to two thirds of the beak which, when combined with the bare faces of some species, creates the illusion that the bird is wearing a balaclava helmet. This sheath reaches it's greatest development in Australian and Melanesian representatives and is often reduced or absent in outlying forms such as on Hawaii.

Balaclava birds are found throughout Australasia, Melanesia, Polynesia and the Orient. A few species have reached as far as Hawaii and Japan. All have a club of bristles at the end of their long, extensile tongues. The majority are nectar feeders, collecting the fluid with their brush-like tongues (although some take insects, berries, and sap).

The purpose of the "balaclava" varies between different species. In some forms, the bare sheath is brightly coloured and plays a prominent role in courtship. With the abundance of spines and toxic secretions produced by much of Spec's Australian flora, it has been suggested that the sheath prevents injury to the inside of the bird's mouth while feeding. Similarly, insectivorous balaclava birds find the structure a useful shield against bee and wasp stings.

Blue-Faced Balaclava (Worgan robusta)

Blue-faced balaclava, Worgan robusta (Eastern Australia)

The blue-faced balaclava is a rather large and unusually robust member of the family. It is an inhabitant of lowland rainforest and moist woodland along the east coast of Australia where it forages on a variety of blossoms as well as taking large insects.

Green-faced Balaclava (Spelaeornis waitomensis)

Green-faced balaclava, Spelaeornis waitomensis (Aotearoa) (See The Waitomo Caves)

Specimens of some of the most spectacular birds ever seen have recently come to light after expeditions to the hitherto poorly sampled rainforests of the Indonesian Archipelago. Among the most striking are the so-called glitterbirds, colorful little balaclavids of the highly speciose clade Kalimantornis. Over twenty-five species of glitterbirds dwell in tropical rainforest habitats from Borneo in the west to the D'Entrecasteaux Archipelago in the east with the highest diversity being on Sulawesi and the Moluccas.

Glitterbirds are highly sexually dimorphic, with the females being fairly non-descript brown or black birds. The males, on the other hand, are phenomenally ornamental, with brilliantly colored feathers. The most spectacular feature is a the large balaclava-wattle that in some species covers the greater part of the head. These are of variable shape between species and may sport a number of projections that can be reconfigured by inflating or deflating air cavities in the wattle. The outermost membrane of the wattle consists of a thin transparent layer of skin beneath which lie clusters of guanine crystals. Sunlight reflecting off these crystals produces a dazzling display of iridescent color that gives these birds their common name. Most males also possess a pair of plastic-like display plumes projecting from their tails, similar to some male bunglebirds.

As far as is known, all species are polygynous breeders. Males may try to entice mates throughout the year except when in moult although the most intense display period usually occurs from August to January. Males display from a fixed perch by calling loudly and inflating their wattles to their fullest extent, shaking it to produce a scintillating effect. Mating is very brief and the females depart to raise the young on their own.

The day-to-day habits of these birds are poorly documented, but they appear to be sedentary birds that feed primarily on fruit and insects. Unlike most other balaclavas, they take little nectar, a diet that usually warrants a more nomadic lifestyle. This sedentary habit probably accounts for their very high degree of speciation in such a small area with whole species or subspecies restricted to individual islands. All glitterbirds retain the ability to secrete poison into adulthood.

Gold-Shouldered Glitterbird (Kalimantornis solstitialis)

Gold-shouldered glitterbird, Kalimantornis solstitialis (Sulawesi)

This tiny gem of a bird is restricted to a small area of montane rainforest in southeastern Sulawesi. Its name-giving golden "shoulders" are in reality its hands, featherless in males except for the air-catching primaries.

Azure-Faced Glitterbird (Kalimantornis chrysaeus)

Azure-faced glitterbird, Kalimantornis chrysaeus (Borneo)

The Azure-faced Glitterbird is one of the largest members of the genus, reaching a length of 24 cm. It is found in lowland and hill forest throughout the island of Borneo. The male is immediately recognizable by its brilliant blue balaclava that possesses four fingerlike projections. These can be puffed up and extended during display. This species does not possess long tail plumes.

Burmese bluemasque (Personavis vespaphaga)

Burmese bluemasque, Personavis vespaphaga (South and southeast Asia)

The Burmese bluemasque (Personavis vespaphaga) is a plump ground-dweller feeds mostly upon fallen fruit and insects, particularly ants and wasps. Bluemasques prey upon these social insects by ramming their heads through the nest's wall and extending their unusually long, bristle-tipped tongues into the nest cavity, lapping up the ants or wasps as they rush to defend their home. Any assaults of stings, jaws, or burning acids have no effect on the bluemasques, protected as they are by the leathery balaclavas that cover their faces.

Green skoshi (Kamifilius nipponensis)

Green skoshi, Kamifilius nipponenis (Southern Japan: Okinawa, Kyushu, and southern Honshu)

The mountain forests of Japan are the home of many birds, one of the most common being the green skoshi (Kamifilius nipponensis), a tiny balaclavid that feeds upon insects and nectar.

In the summers, skoshis subsist mostly on a diet of nectar, which they steal from flowers by puncturing the plant near the ovaries with their slender, needlelike beaks. The birds are also fond of insects, and often eat the bees and butterflies attracted to the flowers they pillage.

Unusual among balaclava-birds, skoshis are not only poisonous as chicks, but retain their toxic flesh into adulthood. Their characteristic green plumage warns predatory birds and other dinosaurs to stay away, but Japan's native pokemurids, the pikachillas, are adept at 'curing' skoshis and other poisonous birds, leaving their corpses to hang on thorn-bushes while the toxins age to impotency. As a result of this predation, skoshis are extremely skittish and keep themselves to the very tip of the forest canopy when not feeding.

Often, the only evidence of the birds' presence is their song, which usually consists of three notes rapidly voiced, followed by a third note, sustained longer and of lower pitch. Some transliterate the song as "tabemashOU" while others write "Dee-dee-dee DUM" and liken it to the first few notes of Beethoven's 5th symphony.

Kikirin (Jimentoria vulgara)

Kikirin, Jimentoria vulgaris (Western Pacific Rim)

The jimentori (Jimentoria or "ground birds"), restricted to southern Korea and the islands of the Pacific Rim, are unusual for balaclavids in being almost entirely insectivorous. Jimentori occupy a generalized insectivore niche, and spend much of their time on the ground, probing the leaf-litter for grubs.

Named for its rattling call, the kikirin is the most common of the jimentori, and ranges across the islands of Japan and the Sakhalin islands, with infrequent accidentals in Korea and mainland China. These birds are quite social, gathering into groups of roughly half-a-dozen to comb the forest floor for insects and millipedes.

Like other jimentori, kikirin are rampant nest-parasites, laying their own eggs in the unguarded nests of other tweety-birds (often balaclava-birds). These eggs, which are actually nontoxic and completely edible, benefit by their association with other, truly poisonous eggs until the time of their hatching. At this time, the kikirin chick throws the other eggs, which have not yet hatched, out, and monopolizes the attention of its cuckolded parents.

                  ,=Twitiaviidae=Twitiavis superciliosus (Black-faced tweety-bird)
                ,|
                |  `=Pseudartamidae=Pseudartamus collaris (Black-collared mistrider)
                |
=Twitiaviformes=| ,=Arborogemmidae=Yerao aureus splendidus (Tasmanian golden treeclutcher)
                | |
                | |                                               ,=Scythrhynchus superbus (Superb scytherbill)
                | |                                             ,=|
                | |                       ,=Therizinorhynchinae=| `=Phoenix mirabilis (Long-fung)
                `=|                       |                     |
                  | ,=Therizinorhynchidae=|                     `=Gracillarus gracillare (Cackler)
                  | |                     |
                  | |                     |                                   ,=R. immaculatus (Immaculate sturdybill)
                  | |                     `=Robustirhynchinae=Robustirhynchus=|
                  | |                                                         `=R. rubicundis (Red-faced sturdybill)
                  `=|
                    |                               ,=Worgan robusta (Blue-faced balaclava)
                    |                             ,=|
                    |              ,=Balaclavinae=| `=Spelaeornis waitomensis (Green-faced balaclava)
                    |              |              |
                    |              |              `=Personavis vespaphaga (Burmese bluemasque)
                    `=Balaclavidae=|
                                   |                ,=Kamifilius nipponenis (Green skoshi)
                                   | ,=Kamifiliinae=|
                                   | |              `=Jimentoria vulgaris (Kikirin)
                                   `=|
                                     |                                  ,=K. chrysaeus (Azure-faced glitterbird)
                                     `=Kalimantornithinae=Kalimantornis=|
                                                                        `=K. solstitialis (Gold-shouldered glitterbird)