Avisauridae

AVISAURIDAE

Home-Earth has an impressive diversity of terrestrial carnivorous flying birds – owls at night, falcons, hawks, buzzards, eagles, ospreys, and so on during the day. All these predators, with the exception of a few megalomaniac songbirds (Passeriformes), kingfishers (Alcedinidae) and frogmouths (Podargidae), belong to the Falconiformes (diurnal birds of prey) and the Strigiformes (owls), two groups of Neornithes that arose in the Eocene or perhaps Palaeocene. Spec's birds of prey, the avisaurs, are somewhat different.

Most immediately noticeable, avisaurs possess of teeth and lack a beak (hooked or otherwise), which gives their heads a surreal drak-like appearance. Also, despite many neornithine-like features in their flight apparatus, they belong to the Enantiornithes, that strange group of 'opposite-birds' that arose in the Early Cretaceous with forms like †Cuspirostrisornis.

(fig. 1) Head of golden flanker, Veraquila chrysaetos

Like all "opposite birds" (Enantiornithes) avisaurs grow very slowly, reaching adult size after several years. This growth pattern is a source of several profound differences to any birds that survive in our timeline.

Avisaur chicks are highly precocial; they leave the nest as soon as they can fly, just a few days after hatching, but they then may take as many as five years to grow to adulthood. Because of this life cycle, every adult avisaur has filled several ecological niches in its life, allowing for low intraspecific competition despite the relatively high numbers of individuals and the rather weak sexual size dimorphism (females commonly being a bit larger than males). As an extreme, an adult (5-year-old) Papuan flanker is capable of killing a Papuan muppet, but when it leaves the nest, at a wingspan of 20 cm, its main food are big insects and the occasional small lizard or marsupial mouse. Consequently, avisaurs are much less diverse than the Home Earth raptors; there are only an estimated 150 or 160 avisaur species, compared to some 480 falconiform and strigiform species in Home-Earth.

(fig. 2) Papuan flanker, Veraquila victor, at the age of a few months

The pentagon chickenhawk (Acioripiter pentagonus), so called after the vaguely pentagonal white spot on the neck of adult males, is just about the only avisaurid species in the forests of eastern North America. Hatching in a nest of up to 5 eggs, the young stay in the tree crowns and hunt first insects, then nonpoisonous birds like jaubs, pickpeckers and otherworld finches like painted pfiffles, then multis and sometimes not-coons, and when maturity approaches around the age of 4 years (and a wingspan of about 1 m), they start to fly fast very close to the ground, pursuing mainly henchicks, as well as nearcrows, and the occasional djad. Large pentagon chickenhawks have even been reported to attack hellrats. Otherworld doves are never safe, but during the nut-glut, chestnut doves form the main part of the diet of over 2-year-old pentagon chickenhawks.

Adult pentagon chickenhawks are very territorial. And if something comes within 10 m of their nest, they become totally furious. It is not advisable to study their nesting behavior without one of those knife- and bulletproof vests and a good helmet.

(fig. 3) Adult female pentagon chickenhawk, Acioripiter pentagonus (Eastern North America)

A southern relative of the pentagon chickenhawk, the pied snakehawk, is common in the skies of southern North America and Central America.

(fig. 4) Pied snakehawk, Acioripiter mexicanus (southern North America and Central America), one year short of maturity

The Pacific coast of northern North America is home to the imperial flanker (Haleuaetus euleucocephalus) with its beautiful white head, neck and tail. However, young individuals could be mistaken for beakless kingfishers. Fish (dead or alive) form the largest part of the diet of this species throughout its life cycle, but an imperial flanker will not refuse other prey of fitting sizes or carrion.

Other species of sea-flankers (Haleuaetus) are distributed pretty much around the world.

(fig. 5) Adult female imperial flanker, Haleuaetus euleucocephalus (Western North America)

Papua is a dangerous place for spexplorers and pretty much everything else except adult Papuan flankers (Veraquila victor). Hatching in a nest of 3 – 4 eggs on top of the rainforest, the little anti-eagles (originally described as a wholly separate species, Antifalco minimus) with their small, straight, conical teeth, soon start hunting big beetles and other insects. (also see fig. 2) One-year-olds have similarly small teeth, but lots more of them, so they can easily pluck the feathers and even the fur off their prey. At this age, cutting edges appear on the teeth. Around the age of 3 years (and a wingspan of about 2 m), tooth shape and number changes again, and the eagles can now cut meat off killed dendrosaurs by means of strongly recurved, finely serrated teeth that are flattened side to side. Fully adult Papuan flankers sometimes hunt terrestrial prey like piggy-beaks or, in rare cases, even Papuan muppets, which they stab from above through the hip bones into the kidneys with claws like a croctiger's.

The golden flanker (Veraquila chrysaetos), which is actually rather brown, rules the skies above all open, landscapes of the Holarctic with suitable perches, thus avoiding competition with the chickenhawks (Acioripiter). The young begin with hunting grasshoppers and big beetles, then for a short period they turn to snails, then to Specworld mice, zams, small lizards and snakes, and then, when the first teeth with serrations grow, to djads, dogbunnies and various henchick species. The largest individuals (with a wingspan over 2 m) have been seen to attack juvenile therizinosaurs, although this behavior is rare.

(fig. 6) Adult golden flanker, Veraquila chrysaetos (Holarctic)

Reaching up to 2 m wingspan, the tiger-necked flanker is the largest of the Australian avisaurs and the ruler of Ozzie woodlands. Adult (5-year-old or so) tiger-neck flankers live mainly off smaller species of brush-runners and hypsies.

(fig. 7) Tiger-necked flanker Veraquila australis (Australia), some 2 years from maturity

Not all avisaurids grow so large, however. The sharp-winged riff (Antifalco abramsi), for example, hardly ever reaches more than 70 cm wingspan. In northern summer, riffs live and breed on the fringes of the prairies of North America, in winter the older individuals migrate to the South American pampas, following much of their prey – small birds that these quick-witted predators catch in mid-air. Even swoops and mistriders are not safe, but the usual prey, especially of young riffs, are jaubs and otherworld finches, followed by the smaller species of nearcrows and otherworld pigeons.

Like all avisaurs, riffs do not care for their chicks past the first few days after their hatching. Unlike other avisaur species, however, in which the adults and young have very little contact, young riffs (those too young to migrate, still lacking cutting edges on the teeth) will sometimes congregate and fly around the adults in sizable swarms. The functions of this "chick-magnet" behavior is unclear, though many researchers hypothesize that the young are feeding off of flying insects flushed up by the adults' hunting.

Riffs can most often be seen in dawn or dusk, generally alone. They rarely vocalize, and when they do so, their call is a muted, cough-like "ugh".

(fig. 8) Sharp-winged riff, Antifalco abramsi (American grasslands)

ALLOSTRIGINAE (Scowls)

Not all avisaurs are day-light predators. The scowls (Allostriginae) have adapted to night-hunting, evolving sensitive night vision, dish-shaped, sound-focusing faces, and silent, silky wings. These birds, have, in essence, taken the place of Home Earth owls.

The striped scowl of northern Eurasia is, from a distance, almost indistinguishable from an owl. On a closer inspection, however, an observer would notice the scowl's un-owl-like feet, and its lack of a beak in favor of a distinctly dinosaurian tooth-filled snout.

Like most avisaurs, striped scowls mate in the winter and lay up to 10 eggs that hatch into precocial young in the spring. These baby scowls soon fly away from their parents' nest and begin to hunt for themselves, progressing through different size-niches as they age, in typical avisaur fashion, until they achieve their adult height of about 60 centimeters after some 4 years. Throughout their lives, striped heds feed upon a variety of small and medium-sized mammals, and occasionally birds and other small dinosaurs.

(fig. 9) Striped scowl, Allostrix rowlingae, with hemming, Xenomarmota sp. (Northern Eurasia)

The willow scowl is a widespread species in temperate North America. Willow scowls are somewhat more diurnal than other scowls, and may often be seen flying through the permanently dark understory of America's old-growth forests.

(fig. 10) Willow scowl, Allostrix diurna (North America)

With a wingspan of over 150 cm, the bob (Pseudobubo atrotugurius) is one of the largest scowls in the world. Even hellrats and young baskervilles are not safe from the adults, though their most common prey are dogbunnies, pseudorats and multis. Especially 2-year-old bobs participate in the nut-glut by stalking sleeping chestnut doves. Bobs don't refuse carrion either. Living in the forests of North America, the bob is known for its blood-curdling call, which in the correct circumstances can sound like laughter played backwards.

A close relative, the Eurasian big-eared scowl (Pseudobubo pseudobubo), lives in the temperate and cold forests of Eurasia.

(fig. 11) Bob, Pseudobubo atrotugurius (North America)

There are also cosmopolitan species of scowls. The spotted scowl (Odontuto maculata), for example, can be found on practically all landmasses except Antarctica and most Pacific islands.

With its 35 cm adult length, the spotted scowl ranks among the smaller scowl species. Juveniles and subadults (up to the age of 2½ years) eat mostly insects and earthworms; with size the amount of small mammals and nonpoisonous birds in the diet increases.

(fig. 12) Spotted scowl, Odontuto maculata (worldwide)

David Marjanović and Daniel Bensen

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