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 #22 – Aepyornis maximus

Along with a lot of unusual mammals, Madagascar was also home to some of the largest birds to ever exist: the giant elephant birds.

Despite being located so close to mainland Africa, these enormous flightless ratites weren’t the closest relatives of ostriches as might be expected. Instead their closest living relatives are the kiwis of New Zealand, and they must have descended from flying ancestors that reached Madagascar across the Indian Ocean sometime during the early-to-mid Cenozoic.

Aepyornis maximus was one of the biggest of these big birds, standing around 3m tall (9′10″) and weighing over 500kg (1,100 lbs). Its eggs were equally massive, up to 34cm long (1’1″) and with a circumference of over 1m (3′3), making them the largest known eggs laid by any vertebrate.

Recent studies of the shape of its brain within its skull show that it had a good sense of smell but very poor eyesight – possibly being near-blind – suggesting that much like its kiwi relatives it was highly specialized for a nocturnal lifestyle.

There were several other species of elephant bird throughout Madagascar, and at least some of them appear to have successfully survived alongside humans for quite some time. Carbon dating of eggshells suggests they were still alive around 1000 years ago, and based on historical mentions they may have persisted as late as the 1600s before finally disappearing.

Eons Roundup

This year I’ve been lucky enough to have some of my work featured in several PBS Eons videos – and I even recently got the opportunity to do some custom images for them! Since I didn’t show any of these off at the time, here they are now:

The basal temnospondyl amphibian Iberospondylus, from “When Giant Amphibians Reigned
https://www.youtube.com/watch?v=rGthtRZl8B0

The flying paleognath bird Lithornis, from “When Birds Stopped Flying
https://www.youtube.com/watch?v=M3h05ajJw0o

The ground sloth Nematherium, from “How Sloths Went From the Seas to the Trees
https://www.youtube.com/watch?v=pt9tBtQoAHo

Happy new year, everybody!