Tag: bird

Island Weirdness #46 — Tyto pollens

The islands of the Caribbean looked very different during the Pleistocene ice ages, when changing sea levels meant larger areas of land were exposed — and one of the most extreme examples of this was the Bahamas, much larger than they are today, with most of the Bahaman Banks exposed and over 10 times more land area.

Tyto pollens was an enormous barn owl, around 1m tall (3’3″), the size of a large eagle and one of the biggest owls to ever exist. It lived in old-growth pine forests on what is now the Andros Island archipelago and preyed mostly on Bahamian hutias, which were originally the only terrestrial mammals in the Bahamas.

It probably evolved in Cuba, and colonized the Bahamas shortly after the hutias did, sometime in the last 400,000 years during a glacial period when a particularly low seal level meant the islands were only about 30km apart.

It was the main nocturnal predator in the Bahamas, and much like its older Italian relative Tyto gigantea it also had a giant hawk counterpart in the daytime: the huge Titanohierax.

Although many popular online sources refer to Tyto pollens as being flightless, it actually had large robust wings and could probably fly quite well. This might be due to some confusion between it and a completely different giant Caribbean owl, Ornimegalonyx.

The Lucayan people probably reached Andros Island sometime around 1000 CE, and coexisted with the giant owls for several centuries. It was only after European arrival in the 1500s and the felling of their forest habitat that they seem to have vanished.

Local legends of an owl-like creature called the chickcharney may have been inspired by historical encounters with Tyto pollens, and suggest that they were aggressively territorial.

Island Weirdness #42 — Tall Owls & Short Ibises

The complete lack of land mammals on the Hawaiian islands left the terrestrial predator niches available to birds — and it was owls who ended up taking advantage of that role in the ecosystem.

The Grallistrix owls were found on Kauaʻi, Oʻahu, Molokaʻi, and Maui, with each island having its own endemic species. They were a type of true owl, probably descended from a species of Strix, and developed especially long legs that led to their nickname of “stilt-owls”.

A stylized illustration of an extinct owl. It has short wings and very long stilt-like legs.
Grallistrix geleches

The Molokaʻi stilt-owl (Grallistrix geleches) was the largest of the four known species, about 60cm tall (2′). Although it had proportionally short wings it was still capable of flying, and probably specialized in stalking and ambushing smaller birds like Hawaiian honeycreepers in the dense forests.

(These owls were also the inspiration for the pokémon Decidueye!)

A stylized illustration of an extinct flightless ibis. It has a downward-curving beak, small wings, and relatively short thick legs compared to other ibises.
Apteribis glenos

Meanwhile the forest floor insectivore niche was occupied by Talpanas on Kauaʻi, but on the other main islands a different type of bird took up the same role.

Apteribis was an ibis closely related to the modern white ibis and scarlet ibis, with three different species found on the islands of Maui, Molokaʻi, and Lānaʻi.

The Moloka’i flightless ibis (Apteribis glenos) was a typical example of the genus, about 50cm long (1’8″). It was flightless, with reduced wings, and had unusually short stocky legs that gave it proportions much more like a kiwi than an ibis. And it probably lived very much like a kiwi, too, probing around in the forest litter with its beak searching for snails and other invertebrates.

We even have an idea of the coloration of these birds, thanks to subfossil remains with preserved feathers. They seem to have been brown and beige, similar to the juvenile plumage of their close relatives.

The arrival of humans at least 1000 years ago would have unfortunately been devastating to both the stilt-owls and the flightless ibises. The combination of hunting, habitat destruction, and invasive dogs, pigs, and rats attacking them and their ground-based nests probably drove them all into extinction very quickly.

Island Weirdness #41 — Talpanas lippa

The big herbivorous moa-nalo weren’t the only unusual waterfowl on the ancient Hawaiian islands — and the island of Kauaʻi had a very odd duck indeed.

The Kauaʻi mole duck (Talpanas lippa) was fairly small, about 50cm long (1’8″), and although it lived alongside one of the moa-nalo species they don’t seem to have been closely related at all. It instead appears to have come from a different duck lineage entirely, with it’s closest living relatives potentially being the stiff-tailed ducks.

It had short chunky legs and an especially weird skull, with eyes so tiny and underdeveloped that it must have been near-blind and flightless. But the areas of its brain associated with the sense of touch were proportionally huge, and although the exact shape of its beak currently isn’t known it seems to have been very wide and flat.

It was probably a nocturnal bird that used an incredibly sensitive bill to grub around in the undergrowth for invertebrates, sort of an equivalent of the modern kiwi but with a face more like a platypus.

The only known Talpanas remains come from mid-Holocene deposits about 6000 years old, but since Kauaʻi is the geologically oldest of the main Hawaiian islands it may have existed there for several million years prior.

Like the moa-nalo it was likely driven to extinction due to human influences on its environment once Polynesian settlers reached the island, sometime between 300 CE and 1200 CE.

Island Weirdness #40 — Moa-Nalo

The islands of Hawaii are part of a larger archipelago formed via hotspot volcanism in the Pacific, and are quite geologically young — the oldest of the main islands was formed just slightly over 5 million years ago, and the youngest less than 0.5 million years ago.

Located almost 3700km (2300 miles) from the nearest continental shore, they’re the most isolated islands on Earth. Their native species are all descended from the rare colonization events that reached such a remote location, either via ocean rafting or island hopping from much older now-submerged islands northwest in the chain.

Like many other Pacific islands no land mammals ever reached Hawaii prior to human arrival, and so it was birds that ended up filling many of the vacant ecological niches.

The dominant herbivores of most the islands were the moa-nalo — no relation to the moa of New Zealand — a group of large flightless birds that resembled giant geese but were actually descended from ducks, with their closest living relative thought to be the modern Pacific black duck. They had reduced wings, chunky legs, and big heavy beaks, some featuring large serrations and others convergently resembling those of giant tortoises.

The Maui Nui large-billed moa-nalo (Thambetochen chauliodous) was one of the biggest species, about 90cm tall (~3′). It originally lived in the highlands of Maui Nui, a large island that formed over 1 million years ago — and when Maui Nui subsided and flooded about 200,000 years ago, it would have then occupied the resulting modern islands of Maui, Molokaʻi, Lānaʻi, and Kahoʻolawe.

Polynesians reached the Hawaiian islands sometime between 300 CE and 1200 CE (the exact dating seems to be controversial). The moa-nalo would have suffered the same fate as many other flightless island birds, lacking any instinctive fear of the new arrivals and falling prey to the invasive pigs, dogs, and rats they brought with them.

Island Weirdness #38 — Sylviornis neocaledoniae

Between Australia and Fiji lie the islands of New Caledonia, an archipelago at the northern end of the mostly-submerged continent of Zealandia. Having split away from Australia at the end of the Cretaceous, 66 million years ago, New Caledonia’s Cenozoic isolation has resulted in the islands acting as a refugium for a number of “living fossil” lineages, including the kagu, a small nautilius, and the “primitive” flowering plant Amborella.

One of the strangest residents of these islands was Sylviornis neocaledoniae, a huge flightless bird standing around 0.75m tall (2’6″) and measuring about 1.7m long (5’7″). Initially mistaken for a ratite, it was later found to be a cousin of the galliforms, the group that contains modern chickens, turkeys, pheasants, quail, megapodes, and curassows.

Sylviornis had a massive skull with a large deep beak, topped with a bony crest, along with reduced wings and stout legs. It also had no wishbone, extra tail vertebrae, and a ribcage and pelvis that looked more like a non-avian dinosaur.

It was probably a slow-moving herbivore, browsing on plant matter and digging up roots and tubers with its beak and feet.

Thousands of subfossil remains of Sylviornis individuals have been found, but a large proportion of them are all juveniles, suggesting that this species’ reproductive strategy was to have large numbers of young at a time. It also seems to have had a surprisingly short lifespan for its size — just 5-7 years.

New Caledonia was first settled by humans around 1500 BCE, and it’s likely that Sylviornis was hunted by both them and the invasive mammals they brought along like dogs, pigs, and rats.

The folklore of the Kanak people features stories of a large flightless bird known as the du, described as being reddish-colored with a star-shaped crest, so it’s possible Sylviornis actually persisted alongside the new arrivals for some time — but eventually the environmental disruption was too much for these odd primitive dino-chickens, and they were gone.

Island Weirdness #37 — Natunaornis gigoura

The islands of Fiji are located in the South Pacific, a couple of thousand kilometers east of Australia and northeast of New Zealand. Formed via volcanic activity, the over 300 islands making up the archipelago had no native land mammals for most of their history, leading to birds, reptiles, and amphibians taking up the large animal niches in the ecosystem.

Subfossil remains of a unique mix of species have been found on Viti Levu, the largest of the Fijian islands — including a flightless megapode, a sylviornithid, a big frog, a giant iguana, a terrestrial crocodilian, and a meolaniid tortoise.

One of the most surprising discoveries, however, was actually a pigeon.

Natunaornis gigoura was by far the biggest pigeon known from any Pacific island, and one of the largest pigeons to ever live, being almost the same size as the Mauritian dodo at around 0.9m tall (3′). But unlike its distant cousin it still looked very much like a scaled-up normal pigeon, probably resembling a giant version of the closely related modern crowned pigeons.

It had reduced wings and strong legs, indicating it was flightless, and an unspecialized beak that suggests it was a generalist forager eating fallen fruit, seeds, and invertebrates from the forest floor.

Natunaornis existed well into the Holocene, but like many other island dwellers it was severely affected by the arrival of humans. Austronesian peoples reached Fiji somewhere between 3500 BCE and 1000 BCE, and it’s likely that a combination of hunting and predation from introduced mammals rapidly killed off the giant pigeons along with all the other large native species.

Island Weirdness #36 — Haast’s Eagle

Before the arrival of humans in New Zealand, the only predator of the native giant flightless birds was Haast’s eagle (Hieraaetus moorei), an enormous species of raptor from the South Island.

With the slightly larger females reaching lengths of around 1.4m (4’7″) and hefty body weights of 15kg (33lbs), it was the largest eagle known to have ever lived, and one of the largest of all birds of prey. Yet its wings were actually proportionally short for its size, spanning about 2.5m (8’2″), giving it less ability to soar but much better maneuverability when flying in the thick vegetation of scrubland and forests.

Its closest living relatives are the much smaller Australian little eagle and the Palearctic booted eagle, which its lineage split from sometime in the Pleistocene — meaning that it must have evolved to be so huge incredibly quickly.

At its size and weight when striking it would have hit its prey with a force equivalent to a falling cinder block, and with no major competitors it could have fed from a single large kill for many days.

As apex predators Haast’s eagles would also have never been particularly numerous, and their population was very sensitive to the availability of their prey species.

Unfortunately the early Māori people also found the large flightless birds like the moa to be delicious easy meals, and by the early 1400s the eagle had disappeared alongside its main food sources. Legends about a giant human-eating bird called the pouakai are thought to be based on folk memory of Haast’s eagle, and it may well have occasionally preyed on the settlers during the short time it coexisted with them.

Island Weirdness #35 — Flightless Giants

With the lack of large terrestrial mammals in New Zealand, birds were free to exploit the “big herbivore” niches in the ecosystem — and the giant moa were the ultimate result.

Closely related to modern South American tinamous, the ancestors of moa were small flying birds that arrived in New Zealand sometime in the early Cenozoic. At the time of the Miocene St Bathans fossil deposits they were already large and flightless, and by the Holocene they had grown truly enormous.

Uniquely they completely lost their wings, not even having the tiny vestigial bones seen in other large flightless birds.

A stylized illustration of an extinct giant flightless bird. It has a tiny head with a downward-curving beak, a long neck, no wings at all, and long chunky legs.
Dinornis robustus

The South Island giant moa (Dinornis robustus) was the largest of them all, with females standing almost 2m tall at the back (6’6″) and able to reach their heads up to heights of around 3.6m (11’10”). It had a long neck, a relatively tiny head with a curved beak, and large powerful legs — and preserved hair-like body feathers show that it was reddish-brown in color.

It also had some of the most extreme sexual dimorphism seen in any bird species, with the males being significantly smaller than the females at only about 1.2m tall (3’11”). This seems to have been the result of scaling-up smaller differences in body size from their ancestors.

A stylized illustration of an extinct flightless bird. It has a triangular downward curving beak, a long neck, small wings, and short stout legs.
Aptornis defossor

The adzebills were another odd group of big flightless birds whose ancestors also date back to sometime before the St Bathans deposits. They had large downward-curving beaks, short strong legs, and highly reduced wings that were smaller proportionally than those of the dodo.

They were less common than the moa, found only the drier forested parts of the lowlands, and based on isotope analysis of their bones they seem to have been predators hunting invertebrates, reptiles, and smaller birds.

When their remains were first discovered they were even thought to be a type of moa, but later studies (including recovered ancient DNA) have shown they were actually gruiformes, with their closest living relatives being either the South American trumpeters or the African flufftails.

The South Island adzebill (Aptornis defossor) was the slightly larger of the two species known from the Holocene, reaching sizes of about 0.8-1m tall (2’8″-3’3″).

The ancestors of the Māori people arrived in New Zealand around the year 1300, and sadly within about a century a combination of human hunting pressure and predation by introduced mammals sent both the moa and adzebills into total extinction.

Island Weirdness #34 — Heracles inexpectatus

New Zealand is probably one of the most famous modern examples of a unique island ecosystem, having been isolated for the last 80 million years. Lacking any living terrestrial mammals, birds instead became the dominant land animals, adapting to a wide range of niches and evolving unusual flightless forms like the modern kiwi and kākāpō.

The St Bathans fossil site on the South Island dates to the early Miocene, about 19 to 16 million years ago, just after a period known as the “Oligocene drowning” when large portions of the landmass were underwater. It gives us a glimpse of an ancient version of New Zealand when the ecosystem was recovering and rapidly diversifying in a then-subtropical climate, and has produced a wide range of new fossil species (including a mysterious mammal).

One of the most recent discoveries from the site is Heracles inexpectatus, a close relative of the modern New Zealand parrots — but significantly larger than any living species, estimated to have stood almost 1m tall (3’3″). Known from just a few leg bones, the fossils were so big that they initially weren’t even recognized as belonging to a parrot, instead being mistaken for a large eagle before their true nature was realized.

At such a size it would likely have been flightless, although it may have still been capable of climbing trees and gliding. Much like the modern kea it was probably an omnivore, using its large curved beak and powerful crunching bite to eat pretty much whatever it wanted.

By the late Miocene, around 13 million years ago, New Zealand’s climate rapidly shifted cooler and drier, and the tropical forests were quickly replaced with temperate ones. This changing habitat may have been too much too fast for the giant parrots to deal with, and they went extinct alongside many of the other St Bathans species.

Buteogallus daggetti

This leggy bird is known as Daggett’s eagle (Buteogallus daggetti), a bird of prey from the Late Pleistocene of southwest North America.

Living between about 2.5 million and 13,000 years ago, it would have stood around 80cm tall (2′7″), with a wingspan of almost 2m (6′6″) and a  fairly hefty body weight of 3kg (6.6lbs). Its feet had less grasping ability than other eagles but it also had particularly strong leg muscles, suggesting it was much better adapted for walking around on the ground.

With its large size, long legs, and terrestrial habits it seems to have convergently evolved to fill the same ecological niche as the modern secretarybird – a grassland-dwelling walking predator that hunted on foot, kicking and stomping small prey animals like snakes, lizards, and rodents.