MOA
When was it declared extinct?
Estimates for the moa's extinction vary, but they are thought to have become extinct in the 1500s.
Where did it spend its time?
The moa can only be found in New Zealand.
(Moa—Several species of moa once roamed the New Zealand islands. They ranged in size from 1-meter-tall, 25-kilogram birds to 4-meter-tall, 275-kilogram giants.)
The elephant birds (see earlier in this chapter) were not the only large birds that roamed the earth recently. The islands of New Zealand, thousands of miles east of Madagascar, were once home to several species of large bird, the largest of which was taller than elephant birds but much more slender. These birds were known as moa (a Polynesian word that means "fowl") and had lived on the islands of New Zealand for tens of millions of years.
Because the only mammals that had made it to New Zealand were bats, the islands were devoid of any large ground-based predators or herbivores, allowing the moa's ancestors to evolve in novel ways. First, because there were no mammalian predators, flying was an unnecessary extravagance, especially given the abundance of food.
Flight limits the maximum size a bird can ever be, and without it, the moa grew to enormous proportions. Second, because there were no mammalian herbivores in New Zealand, the moa evolved to fill the ecological role that animals like deer do in many other parts of the world.
Scientists have identified between 10 and 15 species of moa from their remains, but it is impossible to know how many species of these fascinating birds once inhabited New Zealand's islands. According to some experts, there could have been as many as 24 species of moa. The smallest species stood around 1 m tall and weighed around 25 kg, while the largest species, Din ornis robustus on South Island and Din ornis novaezelandiae on North Island, stood around 4 m tall and weighed 275 kg. Interestingly, moa skeletons and reconstructions are almost always depicted standing upright, but scientists now believe that they walked around with their necks held more or less horizontal to the ground, but they could have probably risen to their full height when necessary. Like the kiwis, the moa were covered in fine feathers that resembled hair, and they all had very robust legs that ended in powerful, clawed feet. The head, throat, and lower legs were mostly featherless. The moa's wings had become completely useless. that they had shrunk almost to nothing, remaining only as small vestigial flaps beneath the hair like plumage.
The moa were all herbivores, and as they evolved into different species, they most likely fed on different plants in different habitats. Some of the species may have grazed on low-growing herbs in the lowlands, while others may have nibbled on low-growing herbs in the uplands. Although New Zealand was once free of mammalian predators, the moa did have an adversary in the form of Haast's eagle (see later in this chapter), an impressive aerial predator that most likely attacked and killed the moa from the air with its powerful crushing talons. The moa's only real defense against this predator was their powerful legs, which gave them a good turn of speed when needed.
The bones and bits of mummified moa tissue that have been discovered tell us where the animal lived and what it looked like, but they only provide a partial picture of the lives of these long-dead animals. The moa, like other birds, laid eggs—large eggs (the largest moa egg has the same capacity as about 100 chicken eggs), and since building a nest up a tree was out of the question, these had to be deposited on the ground, most likely in a simple scrape or on a mound of gathered vegetation. The female moa was much larger than the male, which suggests that they must have had some interesting breeding system that we can only speculate on, but it is reasonable to assume that the female protected a territory and attracted suitors—a reversal of what is seen in many bird species, where the male must attract mates.
What became of these feathered giants? Humans are the simple answer. Polynesians (called Mori) arrived in New Zealand around 1300, and their impact on the plants and animals of these islands was dramatic. We can only imagine what these people thought when they arrived in New Zealand, but they must have been at sea for a long time with no charts and no idea where they were going, so coming across these verdant, volcanic islands stocked with all kinds of food must have been cause for celebration. There is evidence to suggest that these migrants began wildfires, possibly to clear land for crop cultivation or to drive prey animals out of cover. They also hunted the moa directly, and the moa were doomed as a result of the combined effects of this and habitat loss. The moa were most likely long-lived birds, as it has been demonstrated that they only reached full size around the age of 10, with several more years passing before they reached sexual maturity. As a result, any factors that affected the number of adults in the population, such as hunting and habitat loss, had a significant impact on the population as a whole. It has recently been proposed that moa populations were declining prior to the arrival of humans, possibly due to disease spread by errant migrating birds or even explosive volcanic activity. Despite the possibility of a dwindling population, the moas were wiped out around 160 years after humans arrived—a startlingly short period of time and yet another example of how destructive our species can be.
• The kiwis were once thought to be the moa's closest living relatives, but new research shows that they are more closely related to the emu of Australia and the cassowary of Australia and New Guinea.
• It is thought that the moa's ancestors walked across to New Zealand when it was still part of the vast landmass known as Gondwanaland. Over tens of millions of years, tectonic forces ripped New Zealand's lands apart, resulting in an isolated group of islands. The kiwis' ancestors are thought to have migrated to New Zealand after it had become separated.
• New Zealand is an oceanic archipelago comprised of two large islands, the North and South Islands, as well as numerous smaller islands. The land area and diversity of habitats on these islands provided the original inhabitants with a plethora of niches into which to evolve, and birds eventually became the rulers of this realm.
• More than 58 native bird species have become extinct in New Zealand since the arrival of humans. All birds descended from small dinosaurs in the late Jurassic period about 155 million years ago. Ratites, the group of birds that included the moa, evolved in Gondwanaland, which is now known as South America. The ratites evolved into the moa and kiwis of New Zealand, the elephant birds of Madagascar (see earlier in this chapter), the emu of Australia, the cassowary of Australia and New Guinea, the ostrich of southern Africa, and the rheas of South America as this supercontinent was wrenched apart over millions of years.
HAAST’S EAGLE
When was it declared extinct?
The Haast's eagle is thought to have become extinct around 500 years ago, though it has been claimed that the species survived until very recently.
Where did it spend its time?
The eagle can only be found in New Zealand.
(Haast's Eagle—A massive bird that was a specialist predator of New Zealand's extinct moa.)
Birds ruled New Zealand before humans arrived. Many of the islands' feathered inhabitants gave up flying in the absence of mammalian predators, and some of them evolved into giants like the moa (see the entry earlier in this chapter). These islands were a treasure trove of animal prey for the animals that could reach them, and sometime between 700,000 and 1.8 million years ago, some small raptors, very similar to the extant little eagle (Aquila morphnoides), may have been caught in a storm and blown off course, eventually landing in the strange land of New Zealand, where their bird relatives quite literally ran the roost.
This land was ripe with possibilities. Many of New Zealand's native birds were flightless herbivores and omnivores. There was a void in New Zealand for an aerial predator capable of tackling the numerous ground-dwelling birds, and the little lost eagle evolved quickly to fill it. For the most part, evolution moves slowly, but if there is a gap in an ecosystem, a species can evolve quickly to fill it. This is what happened to Haast's eagle's ancestors, who evolved from a small bird of prey into the largest eagle ever to live and the only eagle to be the top predator in its ecosystem.
Haast's eagle, like other top predators, was probably never very common, and as a result, remains of this fearsome predator are scarce. There are three complete skeletons known (the most recent discovered in 1990), as well as numerous fragmentary remains. The bones show how large this eagle was. A fully grown female weighed 10 to 15 kg and stood 1.1 m tall, with a wingspan of approximately 2.6 m. This is approaching the weight limit for a bird reliant on
flapping flight and manoeuvrability. In comparison, the harpy eagle (Harpia harpyja) is the heaviest living eagle, weighing around 8 kg. The skull of Haast's eagle was approximately 15 cm long, but the bill was not as bulky as that of larger, living eagles. Its claws were thought to be extremely powerful, with enormous 7-cm-long talons at the tips.
For its size, Haast's eagle had short wings, which it shared with the harpy eagle. Many eagle species have long, broad wings that allow them to soar effortlessly at high altitude for long periods of time, but long wings would be detrimental to those species that evolved in forest habitats. Stubbier wings are a much better bet in these situations, and it is thought that Haast's eagle was a forest and bush animal.
Haast's eagle must have been a formidable predator with its enormous size, terrifying talons, and manoeuvrability, but what did it eat? At least a dozen moa skeletons have been discovered with gouges and scars in their pelvic bones. Haast's eagle was the top predator in New Zealand prior to the arrival of humans, and the marks on these moa bones are most likely the result of a predatory attack by Haast's eagle. Haast's eagle surveyed its territory for moa and other large, ground-dwelling birds from a perch in a tall tree, and when it spotted a suitable quarry, it launched an attack. Swooping towards the prey at 80 to 100 km/h, it swung its terrible talons forward in preparation for the contact. The force of the impact was absorbed by the eagle's powerful legs, but the prey was most likely knocked off its feet. If the initial strike wasn't enough to kill the prey, the piercing force of eight massive talons caused massive internal bleeding, and the victim died soon after from blood loss and shock. With its prey dead, the eagle tore the skin of the unfortunate victim before digging into its flesh with its talons and beak.
The large living eagles usually take prey that is much smaller than themselves so that they can carry it away to a safe perch away from scavengers. Because there were no scavengers large enough to challenge a Haast's eagle for its kill in New Zealand, it could tackle large prey and eat them where they died. The only animals a Haast's eagle feared at a kill were others of its kind.
Even though it was a formidable predator, the Haast's eagle was no match for humans, who arrived in New Zealand around the year 1300. It is now widely accepted that humans caused the extinction of the moa and many other unique New Zealand birds through hunting and habitat destruction. Humans undoubtedly saw and knew this raptor, and whether they feared or admired it is debatable. Humans persecute top predators in some cultures around the world, while these animals are revered in others. Perhaps the Mori hunted Haast's eagle as an act of reverence, not only because it competed with them for food. Many aboriginal cultures collect and wear the body parts of powerful predators in the belief that the animal's strength will be transferred to the wearer. Hunting and dwindling prey most likely killed the Haast's eagle before the last moa vanished.
• For a long time, it was assumed that Haast's eagle evolved from the Australasian wedge-tailed eagle. Scientists recently extracted DNA from Haast's eagle bones and compared it to DNA from living eagles. It was discovered that the little eagle is the closest relative of Haast's eagle. Constructing a family tree from ancient DNA should be approached with caution because thousands of years in the ground can severely damage DNA, and old samples can be contaminated with DNA from sources too numerous to list.
• Charles Douglas, a famous New Zealand explorer who was not prone to exaggeration and flights of fancy, claimed in his journal in the 1870s that he had an encounter with two giant birds of prey in the Lands borough River Valley of South Island. If this is true, could Haast's eagle have survived in a remote part of New Zealand until relatively recently? We'll never know the truth because Douglas killed and ate both of these mysterious birds.
• The bones of another massive raptor have also been discovered in New Zealand, and they are now thought to have belonged to a massive type of harrier. Harriers are small birds of prey that weigh around 700 g. The New Zealand giant harrier (Circus eylesi) weighed around 3 kg.