bird – Nix Illustration

Avisaurus

Avisaurus darwini here lived at the very end of the Cretaceous, about 66 million years ago, in what is now the Hell Creek fossil beds in Montana, USA.

It was a member of a diverse group of Mesozoic birds known as enantiornitheans, which retained claws on their wings and often still had toothed snouts instead of beaks – and being part of the avisaurid family it was also one of the larger known examples of these birds, similar in size to a modern hawk at around 60cm long (~2′).

Although this species is only known from isolated foot bones, the remains have distinct enough anatomical features to show that Avisaurus had powerful gripping talons similar to those of modern hawks and owls, suggesting it had a similar lifestyle hunting small vertebrate prey in the ancient swampy Hell Creek ecosystem.

Spectember 2024 #03: Terrible Toucan

This concept comes from thecomiccreator, who suggested a “carnivorous/omnivorous toucan”:

A shaded sketch of a speculative descendant of toucans, shown both standing on one leg and in flight. Its a stork-like bird with a massive long serrated beak, a bald vulture-like head and ruffed neck, large broad wings with slotted flight feathers, and long legs with two forward-facing toes and two backwards-facing toes.

Descended from toco toucans inhabiting savanna grasslands, Deinotukan auctorcomicus is a large stork-like bird standing about 1.2m tall (~4′).

Unlike its mostly-frugivorous ancestors it’s primarily a scavenger, soaring on thermals with its long broad wings and following vultures towards sources of carrion. Its massive serrated beak allows it to efficiently open up tough-skinned carcasses, and with its nostrils positioned up near its eyes it can probe around inside much deeper than other scavengers while still being able to breathe.

It also opportunistically hunts live prey, especially during the breeding season while raising chicks, slowly stalking around on foot snatching up anything small enough to fit in its mouth and be swallowed whole.

Its beak contains an extensive network of blood vessels, which along with the large surface area make it an effective way of shedding excess heat in its hot tropical habitat – but when soaring at high altitudes where temperatures are near-freezing it’s also able to shunt blood flow away from its beak to conserve body heat instead.

Xenerodiops

Xenerodiops mycter was an unusual heron from the Oligocene (~30 million years ago) of what is now Egypt.

Known only from a partial skull and an arm bone, it’s estimated to have stood around 70cm tall (~2’4″) and was probably fairly similar in overall appearance to modern night herons. Its beak was powerfully built and had a distinctive downwards curve, shaped more like some types of stork than other herons – suggesting it may have had a convergently stork-like lifestyle, slowly walking through its marshy habitat probing around for prey and snapping up whatever its beak came into contact with.

Patagopteryx

While birds are one of the few animal groups to have achieved powered flight, they’re also very prone to losing their aerial abilities. Many times over their evolutionary history, multiple different bird lineages have convergently become secondarily flightless – and Patagopteryx deferrariisi was one of the earliest known examples of this.

Living during the Late Cretaceous, about 86-84 million years ago, in what is now the northern part of Argentine Patagonia in South America, Patagopteryx was roughly the size of a modern chicken at around 50cm long.

When it was first discovered it was classified as a ratite, but soon after it was recognized as actually being a much earlier type of bird, an early ornithuromorph only distantly related to any modern groups.

It had small wings, little-to-no keel, and no wishbone, indicating it lacked the large powerful musculature required for flight. Its legs were quite long, with large feet with all four toes facing forward – proportions that suggest it was built more for walking than for high-speed running.

Growth rings in its bones also show that it had a much slower growth rate than modern birds, taking several years to reach adult size.

Miomancalla

The mancallines were a lineage of flightless semi-aquatic birds closely related to auks. Known from the Pacific coasts of what are now California and Mexico, between about 7.5 and 0.5 million years ago, they convergently evolved a close resemblance and similar lifestyle to both the recently-extinct North Atlantic great auk and the southern penguins.

Miomancalla howardi here lived in offshore waters around southern California during the late Miocene (~7-5 million years ago). The largest of the mancallines, it just slightly beat out the great auk in size – standing around 90cm tall (~3′) and weighing an estimated 5kg (11lbs).

Like great auks and penguins it would have been a specialized wing-propelled diver, swimming using “underwater flight” to feed on small bait fish. It probably spent much of its life out at sea, probably only returning to land to molt and breed.

Spectember/Spectober 2023 #09: Things With Wings

(Apologies for the abrupt absence – I’m okay, just having everything break down at once. ~~This is fine.~~)

So— back to the speculative evolution request list!

TheBigDeepCheatsy requested a “cactus-dwelling/germinating evolution of introduced rosy-faced lovebirds”:

A shaded sketch of a speculative symbiotic relationship between lovebirds and saguaro cactus. The lovebird is shown on the left, a small parrot that looks very similar to modern rosy-faced lovebird except with hints of a more mottled color pattern. The cactus is shown on the right, a large fasciated saguaro with its top fanning out into a wide "crown", with several nest holes dug into it and multiple lovebirds occupying them.

While Agapornis cheatsyi is still quite physically similar to its introduced ancestors, this lovebird has developed a close symbiotic relationship with the cactus Carnegiea ornipolis, a descendant of the modern saguaro.

Naturally fasciated, this cactus grows a splaying fan-like crown which the lovebirds excavate their shallow nest burrows into. Feeding on the cactus’ fruit in early summer, the lovebirds then disperse the seeds via their droppings – a process that significantly improves propagation chances, both due to the birds commonly foraging and defecating around suitable nurse plants and the passage through their gut speeding up germination.

Someone calling themself “LB” asked for some “flying afrotherians”:

A shaded sketch of a speculative flying tenrec. It's a bat-like animal with membranous wings supported by three elongated fingers, and a large shrew-like head with long toothy jaws and an elephant-shrew-like nose.

Elbeitandraka venenifer is a descendant of tree-climbing Malagasy tenrecs that developed gliding membranes – and its lineage is now just about achieving true powered flight.

About 25cm long (~10″), its proportionally short broad wings require it to fly very fast to generate enough lift for its weight. It mostly only actively flies when traveling between roosts and feeding sites (or when escaping from threats), alternating between gliding to save energy and flapping to recover altitude.

It’s an opportunistic omnivore, crawling around in the tree canopy foraging for vegetation, fruits, fungi, invertebrates, and the occasional smaller vertebrate, using its flexible sengi-like nose to probe around in crevices.

Much like modern common tenrecs it’s capable of hibernating for months at a time through periods of scarce food availability. It also accumulates alkaloid toxins in its body from its arthropod prey, advertising its unpalatability to predators with bold contrasting warning coloration on its wing membranes.

And here’s a combination of a couple of anonymous requests for both “flying heterodontosaurs” and “dragons with hind leg wings, a la sharovipteryx”:

A shaded sketch of a speculative flying predatory heterodontosaurid dinosaur, show both on the ground in a quadrupedal posture and in flight. Its hind legs form its main wings, with elongated outer toes supporting large pterosaur-like flight membranes. It also has a hooked beak at the front of fanged jaws, an s-curved neck, a compact fuzzy body, short forelimbs with taloned hands and small stabilization membranes, and a long vaned tail.

Inversodraco rapax is a highly specialized Jurassic descendant of heterodontosaurids that took to climbing and gliding, developing delta-wing-like membranes on their hindlimbs convergently similar to those of the earlier sharovipterygids.

Around 75cm long (~2’6″), it has unusually flexible hip joints for a dinosaur, able to splay its legs out to the sides to deploy wings supported by an elongated outer toe on each foot. Its arms form small forewings for stability, and its long tail ends in a vane of stiffened feathers that aid in steering.

Unlike its herbivorous-to-omnivorous ancestors it’s primarily a carnivore, swooping down onto small prey and grabbing it with its talon-like forelimbs.

Spectember/Spectober 2023 #07: Terror Eagle

September might have ended, but guess what? I am not remotely done with this yet so we’re continuing on.

Now it’s Spectober.

(Also just a reminder: I am not currently taking new requests. I’ve got far too many existing ones that I’m still working through!)

Someone who identified themself only as “Adam” asked for “eagles evolving into terrestrial predators to pursue larger prey”:

A shaded sketch of a speculative flightless eagle. It has a large head with a big hooked beak, with the skin on its head and neck only sparsely feathered like a vulture. It's body is chunky and covered in shaggy feathers, and it has thick legs and stumpy tail. Its small vestigial-looking wings have a large bony knob growing from just below the wrist joint.

A flightless eagle occupying an apex predator niche in the same island chain as the giant herbivorous tegu, Terraetus adamii is descended from a species similar to the modern harpy eagle. It isn’t substantially larger than the biggest modern eagles – standing about 1.2m tall (~4′) – but it’s certainly much more massive, weighing around 25kg (~55lbs).

In the absence of other large terrestrial predators its ancestors originally took up a caracara-like lifestyle, preferring hunting on foot over flying, before gradually becoming totally flightless and converging on terror birds with large heavy skulls, reduced wings, and powerful legs.

Terraetus’ head is only very sparsely feathered, an adaptation for feeding inside the carcasses of large prey, which it dispatches using a combination of kicking and blows from its large hooked beak. It’s usually a solitary hunter that can tackle prey up to two or three times its own weight – preferencing the juveniles of the herbivorous tegu – but during the breeding season pairs will occasionally hunt cooperatively to take down larger targets.

Despite possessing sharp beaks and talons, these weapons aren’t actually used in fights between individuals of this species. Instead they bodily shove each other back and forth, battering at each other with large bony knobs that grow from the hand bones of each wing.

Spectember 2023 #04: Some Aukward Birds

An anonymous submitter asked for a “penguin/auk-like relative of Pelagornis“:

A shaded sketch of a speculative flightless seabird related to the extinct "pseudotooth" bird Pelagornis. It has a long slender beak with serrated tooth-like edges, a penguin-like body, flipper-like wings, large webbed feet, and a stumpy tail.

Odontopinguinus vomitus represents an unusal early branch of the pelagornithids that didn’t take up long-distance soaring, instead specializing for a pursuit diving lifestyle convergently similar to that of the contemporaneous early penguins, and the later auks and plotopterids.

About 1.2m tall (~4′), it has a more slender spear-like beak than its relatives, with forward-pointing pseudotooth serrations. Like other pelagornithids these “teeth” are fairly fragile, so it feeds primarily on soft-bodied fish and squid, pursuing them underwater with wing-propelled underwater “flight”.

Much like procellariiformes they’re also rather stinky birds, producing musky preen oil and projectile vomiting foul-smelling stomach contents at threats and rivals.

And another anon wanted to see a “big flightless marine duck”:

A shaded sketch of a speculative flightless marine duck. It has a goose-like beak with protruding comb-like structures at the sides (giving it the superficial appearance of having teeth), a long neck, a long loon-like body with vestigial folded wings, large cormorant-like webbed feet position far back, and a short tail.

Thalassonetta anambulatus is descended from the already mostly-flightless steamer ducks. At around 2m long (6’6″) it’s massive for a waterfowl, with vestigial wings and large webbed feet used to propel itself while diving.

With its rather elongated and heavy body and loon-like leg configuration it’s no longer able to walk on land – and it’s actually almost fully aquatic, only awkwardly hauling out into isolated island beaches to molt and breed.

It feeds mainly on molluscs, crustaceans, and other marine invertebrates, using the large lamellae in its bill to strain them out of soft seafloor sediments.

São Miguel Scops Owl

When owls find their way onto isolated islands lacking any terrestrial predators, they have a tendency to take up that role for themselves – evolving longer legs and shorter wings, and specializing more towards hunting on foot. From New Zealand to Hawaii to the Caribbean to the Mediterranean to Macaronesia, leggy island ground-owls have independently happened over and over again in the last few million years—

—And, unfortunately, they’ve all also become victims of the Holocene extinction, their fragile island ecosystems too easily disrupted by human activity and the arrival of invasive species.

The São Miguel scops owl (Otus frutuosoi) was found only in the Azores on São Miguel Island. About 18cm tall (~7″), it was slightly smaller than its relative the Eurasian scops owl, with longer legs, a wider body, and much shorter wings.

Its wing proportions indicate it would have been a poor flyer, instead primarily hunting on foot in the dense laurisilva forests. Since there were no terrestrial mammals or reptiles on São Miguel at the time, its diet probably mainly consisted of insects and other invertebrates – and it would have in turn been the potential prey of larger predatory birds like buzzards and long-eared owls.

All currently known subfossil remains of the São Miguel scops owl date only from the Holocene, between about 50 BCE and 125 CE. It’s likely that it was extinct by the 1400s, following the settlement of humans in the Azores, destruction of its forest habitat, and the introduction of rodents, cats, and weasels.

Danielsraptor

The evolution of falcons is rather poorly understood. Thanks to genetic evidence we know that they’re closely related to seriemas, parrots, and passerines, but their fossil record is patchy and little is known about the early members of their lineage.

But a group knows as masillaraptorids are giving us a rare glimpse at what some early falconiforms were up to. Known from the Eocene of Europe, these long-legged predatory birds seem to have been caracara-like terrestrial hunters specializing in chasing down prey on foot – although their wings and tails indicate they were also still strong fliers.

Danielsraptor phorusrhacoides lived during the early Eocene, about 55 million years ago, in what is now eastern England. Although only known from partial remains, it was probably around 45-60cm long (~1’6″-2′), and it had a large hooked beak with a surprising amount of convergent similarity to those of the flightless South American terror birds.

Its mixture of falcon-like and seriema-like features may indicate that the common ancestor of both of these bird groups was a similar sort of leggy ground-hunting predator.