The Living Planet (1984) s01e10 Episode Script
Worlds Apart
Blue water covers most of our planet, but in it are set tiny specks of land, some the tips of volcanoes, some mere rings of coral.
They're miniature enclosed worlds where animals and plants become transformed into new species with extraordinary speed.
If you wanted to pick a really remote desert islan cut off from the rest of the world, you might well choose this one.
This is Aldabra in the Indian Ocean.
The nearest land in that direction is the coast of Africa, about 250 miles away.
Over there, about the same distance, is Madagascar, and if you sailed in that direction, you wouldn't hit much until you got to the coast of Australia 4,000 miles away.
The island is the tip of an extinct submarine volcano that rises 15,000 feet from the bottom of the Indian Ocean and is capped with coral rock.
When it finally rose above the surface of the sea about 50,000 years ago, it was lifeless, but now, a mere 50,000 years later, well, just look.
Frigate birds, thousands of them, circle above one end of the island.
They've come from all over the Indian Ocean, even from India itself 2,000 miles away, to nest on this particular island in the mangroves.
The white-headed birds among them are immatures, and there are two different species of them, one bigger than the other.
The males inflate their scarlet throat pouches to show that the site is taken, and to attract the female.
When she arrives, he persuades her to stay with ecstatic shakes of his head.
Red-footed boobies are here, too.
They're great travellers, and their chicks, which are already fledging, may well be fishing 3,000 or 4,000 miles away within a year.
Noddies nest not on Aldabra but on a neighbouring atoll, building platforms of seaweed in the Pisonia trees, and beneath, on the open coral sand, two million sooty terns lay their eggs.
Their vast numbers are an indication of the richness of the surrounding sea.
Every day, the birds take from it many tons of small fish, little squid and other marine creatures.
The atoll itself provides no food for them.
All a pair of sooty terns seek from it are a few square inches of dry land on which to place their single egg, and an absence of cats, rats and all other egg-stealers and chick-eaters that plague nesting sites on the mainland.
Such security is important to these terns, for not only do they lay their eggs exposed and unprotected on the ground, but their young remain flightless for several weeks after hatching and a hungry cat could cause havoc among them.
So terns find it well worthwhile, for the sake of such security, to fly hundreds of miles to this island.
The plants that grow on remote islands like Aldabra how do they get here? Well, some certainly come by sea.
In a short walk along this high-water mark, I've picked up already three different kinds of seeds.
Here's the biggest floating seed of them all.
This is a coconut.
There's the familiar nut which contains the white flesh, and this husk, from which we sometimes make coconut mats, is the flotation device.
Nuts like this can float in the sea for up to four months.
This one is dead but here is one that's alive and still sprouting The green stem springing from the top, a white rootlet striking down underneath.
Under natural conditions, coconuts establish themselves at the head of the beach.
As they grow taller, they lean out over the sand so that when they're full-grown, their nuts will drop within reach of the high tide and be washed out to sea to spread to other islands.
A land-living animal also reached here by sea.
The time and place to find it is at night among the coconut groves.
It travelled here as a larva in the same way as the coconuts, floating in the surface waters.
One or two in a million were washed up on the beach and crawled ashore to live on land among the coconuts, feeding on them.
It's almost the only creature here likely to give you a painful bite, so it needs tackling with care.
It's the coconut crab.
Its legs are so long that it can embrace the trunk of a coconut palm, and it has no difficulty in clambering up to the top.
There it cuts down young nuts with its pincers, and returns to the ground to feed on the soft white coconut flesh.
Crabs as a group are sea-living creatures and breathe in water by means of gills.
To breathe in air, the coconut crab has developed large pouches within its shell that have moist linings and can act as simple lungs.
But when it breeds, it has to return to the sea.
There it releases its eggs and sperm into the water at high tide, so that its larvae will circulate through the sea, and may be washed up on some new island.
One exceptional land animal made the voyage to Aldabra as an adult: Its most famous inhabitant, the giant tortoise.
Most tortoises are naturally buoyant.
If one on the coast of mainland Africa, grazing among the mangroves, were swept out to sea, it might survive long enough to be carried by currents to the islands of the Indian Ocean, and later to spread among them.
That, almost certainly, is how ancestors of the Aldabran giant tortoise reached here.
It's not a very hospitable place for animals like tortoises that feed on land-living plants.
The coral rock which forms the substance of the island erodes into a honeycomb of wickedly sharp blades and spikes.
Any creature moving over it has to step with care if it's not to cut itself badly.
Here and there, the rock forms deep pits into which tortoises sometimes tumble.
When that happens, there is no escape, and the trapped animals, even if they survive the fall, die from starvation Quite apart from such traps, the island is a harsh, taxing place in which to live.
The tropical sun, beating down on the animals, threatens to bake them alive inside their shells, and the remains of casualties are common.
So as the day heats up, the tortoises head determinedly for the few trees that can provide shade.
Here and there on some beaches grow low, windswept Guettarda trees.
By noon, the ground beneath their branches is packed with refugees from the sun, waiting for the temperature to fall so that they can search for edible leaves.
Birds, too, can overheat.
The frigates swoop over the one almost permanent lagoon of rainwater on the island, snatching sips from its surface.
Tortoises, too, must have fresh water.
Although they don't drink every day, they must do every week or so if they're to survive.
Water can also cool an overheated body.
As the dry season progresses, the water evaporates and the pools get smaller and more crowded.
Many that came here for relief are near the end of their strength.
Some are unable to drag themselves out of the mud, and so die of starvation.
And yet, in spite of all these hardships, the tortoises breed and proliferate.
There are some 150,000 of them on the atoll.
Their staple food is vegetation and they crop the grass right down to the rootstock.
But as island animals everywhere tend to do, they've broadened their taste in food to include almost anything that is edible, including the carcasses of their dead companions.
Flesh is too nutritious to be allowed to rot and go to waste in this land where there is so little to eat.
50,000 years, which is the time, apparently, that Aldabra has been above the sea, is not a very long time in terms of evolution.
Nonetheless, 50,000 years of isolation on the island has brought changes to many plants and animals that live here.
They've begun to take on their own character, so now they differ slightly both from the ancestors which colonised the island and from their nearest relations elsewhere in the world.
For example, this close-cropped withered turf around me contains about 20 different species of plants.
All have been relentlessly cropped by giant tortoises like that.
And look, for example, at this little sedge.
Most sedges bear their flowers at the top of stems that rise quite high above the leaves.
Flowers sticking up like this would not survive long on Aldabra.
The tortoises would eat them.
These Aldabran sedges bear their flowers and develop their seeds close to the rootstock where the jaws of the hungry tortoises can't reach them.
The changes that take place in an island species are not always directly useful like that.
Another of Aldabra's plants has changed in a way that seems to have no practical significance at all.
This is a lily called Lomatophyllum.
It's slightly different in colour from Lomatophyll growing elsewhere, but that's all.
The difference is very trivial.
But some island plants are spectacularly different from their nearest relatives.
Very, very rarely, extraordinary double nuts like this are washed up on the shores of the coral islands of the Indian Ocean.
For centuries, nobody knew where they came from.
Some said they were produced by fantastic palm trees that grew under the surface of the sea, so they were called coco-de-mer.
People believed that their kernels could be made into irresistible love potions and that their shells, when turned into a cup, would render the most powerful poison harmless.
A single nut like this was literally worth a king's ransom.
It wasn't until the 18th century that people discovered that the palms that produced these nuts grew in one tiny group of islands in the Seychelles, some 700 miles from Aldabra.
The largest surviving group of these trees stands on the little island of Praslin.
There are male and female trees.
The males produce small yellow flowers on long spikes, and on them lives a little gecko, feeding on their nectar and pollen.
Once again, it's an island original, slightly different in colour from others in neighbouring islands.
The female flowers start as small reddish buds, no bigger than a man's fist, but they will develop into the biggest seed produced by any plant.
It takes seven years for the nuts to develop, and when they are mature, they are so large and so heavy that almost the only way of opening them is with a saw.
Inside, you can see how very different they are from coconuts.
Not only do they have two lobes to them, but the nut itself is full solid with flesh.
Flesh that is so heavy that these mature nuts won't float in sea water.
Indeed, sea water kills them.
And that means two things.
First of all, that these palms have never been able to spread to other islands, and secondly, that they must have actually evolved here.
Isolation changes not only plants but animals.
On Aldabra, wandering among the tortoises are sacred ibis with light blue eyes.
Others elsewhere have dark eyes.
The Aldabran ibis breed among themselves and feed on small shore creatures.
Land crabs are far too big to be eaten, but they have to be pecked to clear them out of the way.
Several species of Aldabran birds have developed slight variations that make them unique.
The kestrel here is slightly smaller than the Madagascar species, but otherwise the same.
The Aldabran sunbird, however, is a little darker than its African relations.
But perhaps the most dramatic and certainly the most endearing quality brought to some of the birds of Aldabra by isolation is this.
Not only extreme tameness, but flightlessness.
This is the Aldabran rail.
Flying takes a lot of energy.
It's of obvious value when escaping ground-living enemies, but there are no such enemies on Aldabra or other remote islands.
So some birds that reach such islands by air have given up flying.
Their wing muscles have dwindled and they can't fly even if they wanted to.
The Aldabran rail is only one example.
A kind of pigeon once lived on another island in the Indian Ocean: Mauritius.
It, too, became flightless and grew as big as a turkey.
It was so tame that European sailors were able to kill it with clubs.
They called it the dodo, and in less than 200 years after finding it, they'd exterminated it.
Grazing alongside the dodo in Mauritius, and living in other islands in the Indian Ocean as well, were giant tortoises.
They, too, were taken for food by seamen and were exterminated.
But Aldabra is so remote that few ships come near it, and here alone, the tortoises have survived.
It seems likely that the African ancestors of these creatures were of a normal size, and that these tortoises became giants as a consequence of living on islands.
Isolation may have had another effect on the tortoises as well.
When African tortoises are threatened, they behave in the same way as this baby Aldabran tortoise.
They first pull in their head, and then they pull after it their heavily armoured front legs so that nothing sticks out and they're comparatively safe from their enemies.
But when the Aldabran tortoise grows up, its proportions change, as this one's have done.
This one is now so big that these huge legs won't fit into this space, so that whatever it does, something sticks out.
It's a fair bet that if there was a hyena on the island, it would make a meal of the giant tortoise.
But there isn't on Aldabra, so this creature's saf Just why the island tortoises should have grown so huge, and another species has done the same in the Galapagos islands, is by no means clear.
It may be that a large animal with big reserves of fat is better able to survive bad seasons when there's little to eat.
It may even be that with no predators on the island, these long-lived creatures just go on growing, but it is not a phenomenon that is restricted to tortoises.
On an island 3,000 miles away from Aldabra, there is another giant reptile.
Komodo is a small island in Indonesia.
From here, back in the 1920s, came stories of a huge lizard that became known as the Komodo dragon, and here the dragons still live.
It's not difficult to find them.
All you need is the carcass of a goat, preferably decayed and smelly, and the scent will attract them from miles around.
It used to be thought that these very big ones were entirely scavengers, relying on what carrion they could find, but now we know that actually they are active killers.
They attack and kill goats, young buffalo, and even on occasion, man.
The reason that I can stand here with relative safety is that their eyesight is not very good, they are almost deaf, and they rely on their senses, primarily on that big yellow tongue which flicks out and tastes the air.
So with any luck, the smell of these dead goats is more powerful than mine, so they will take no notice of me.
They are, in fact, the kings of their island.
They are the top predator.
There is nothing here which preys upon them and is bigger, and nothing with which they have to share their food.
So, from that point of view, there is no reason why they shouldn't grow big.
And the fact is that there is a positive advantage in growing big, because the big ones are getting the bigger share of the food.
Not only that, but we now know that these big ones eat small ones.
That perhaps is a reason why, in the isolation of their island, these kings of Komodo have grown so huge.
And they are indeed immense.
They're related to the water monitors of Asia and Africa and the goannas of Australia, but they are much more massive, for whereas two-thirds of the length of these other monitors is taken up by a long thin tail, the dragon's tail is only about half its length.
Big ones like this can weigh up to 100 pounds and grow to over nine feet long.
Komodo is not, like Aldabra, a coral atoll growing on the drowned tip of a submarine volcano, but the eroded remains of one that stood many thousands of feet above sea level.
Volcanoes, indeed, have built many of the most isolated islands.
The Hawaiian islands, lying in the eastern Pacific, are all volcanic, and the biggest and newest of them is still erupting.
Torrents of basaltic lava erupting from vents 10,000 feet up on the mountain sometimes flow for many miles down the volcano's flanks.
When, eventually, they cool and solidify, they become vast slopes of black naked rock.
Such areas as this may remain virtually sterile for decades.
Some vents produce vast quantities of granular ash which builds up around them into cones.
Plants have a better chance of getting root on such material, and within a century or so, the ash slopes may be covered with green.
These high islands collect moisture-laden clouds, and on the windward side, rain falls very heavily indeed.
Streams flowing down the mountainside cut through the layers of loosely compacted ash, eroding deep valleys.
So, unlike a coral atoll, which is a plain platform of coral, sand and rock only a few feet high, these immense volcanic islands of Hawaii offered their colonists a great variety of habitat from high cold slopes of ash on the summits to well-watered valleys, hot, lush and humid, near sea level, from new, naked basalt to long-established forest growing on ancient lava flows.
To exploit them, the animal colonists changed not into just one new form, but into a multitude.
This bird, the palila, is one of a large family of closely related Hawaiian birds, the honeycreepers.
Their ancestors were probably finch-like birds that were swept here, perhaps by a freak storm many thousands of years ago.
Once here, they developed into over 30 different species, each with its own diet and habitat.
The palila lives largely on seeds and has the short, powerful beak needed to open and crack them.
The 'amakihi, while there's no doubt that it and the palila are related, has a slender beak, suited to picking up small insects and sipping nectar from shallow flowers.
Some species have developed striking feather colours and adornments.
These enable the male and female to identify one another so they don't interbreed with near cousins, and the species becomes increasingly distinct.
So the 'apapane not only has a longer beak to suit its almost exclusive diet of nectar, but a conspicuous red head.
The 'akohekohe lives on a mixed diet of insects and nectar, and has developed a little crest of white feathers at the base of its beak.
The 'i'iwi is scarlet and has a particularly long curved bill that allows it to probe deep into trumpet-shaped flowers such as giant lobelias and bananas.
And perhaps most engaging of all, the akiapolaau, with a splendid dual-purpose beak, the lower mandible pick-like to chip away bark to find insects, and an upper mandible elongated into a probe with which to winkle them out.
It's located a beetle larva burrowing away within the bark.
Look how dexterously it uses the two halves of its beak for these different purposes.
The situation amongst Hawaii's insects is even more extreme than it is among its birds.
There is a kind of fly called Drosophila.
It's found in many parts of the world.
In North America, for example, there are about 200 species, but in these tiny islands of Hawaii, there are at least 800.
It seems that soon after the islands' formation, one or at most two species of Drosophila reached the islands, and they found the same situation as the honeycreepers found, a lot of vacant niches.
And so they evolved to fill them, and they are now Drosophila, the larvae of which feed on fruit or rotting leaves or fungi, or bark or even spiders' eggs.
But now the situation becomes more complex because in Hawaii, there are lava flows like this, and such lava flows often isolate patches of ancient forest like that over there, and in one small patch of forest, there may well be one particular species of Drosophila that occurs nowhere else.
And there are some just there.
These particular ones belong to a group which have evolved, in their isolation, an extraordinary courtship behaviour, just as some honeycreepers have evolved bright colours.
It's an insect equivalent of the arena display of antelope.
The males maintain tiny territories and display and battle with one another.
Instead of antlers, they've developed heads shaped like mallets.
In another species, the male courts the female by hoisting his abdomen over his back and showering her with an aphrodisiac perfume.
Isolation has also affected the wings of Hawaiian insects.
Flying on an island is dangerous.
It risks being blown out to sea, and this extraordinary bug never takes to the air.
Its wings are tiny, and used only for flirting in courtship.
This lacewing can't even use them for that.
Its wings have become fused together to form a shell.
The Hawaiian cranefly has lost its wings completely.
This cranefly's taste for fruit is typical of its family, but other insects have changed their feeding habits.
This flightless bug has adopted the hunting techniques of the mantis which never naturally reached the island.
And this fly is going to get a shock.
The twig caterpillar doesn't, like most twig caterpillars elsewhere, feed on leaves, but has become a carnivore.
It detected the fly with tiny hairs on its back en They trigger the caterpillar to arch backwards and pounce on whatever touched it.
So isolation, by restricting the kinds of creature that reached Hawaii, allows those that did great freedom to develop into different and unexpected forms.
Human beings, the Polynesians, reached Hawaii several thousand years ago.
When Europeans arrived, they found to their surprise an unknown people with an elaborate and splendid culture.
The Hawaiians were superb seamen.
They not only paddled dugout canoes, but sailed immense ocean-going double canoes that could carry several hundred passengers, and that tradition survives still in many parts of the Pacific.
The last of the really big canoes must have disappeared about 100 years ago, but still, in the remoter parts of the Pacific, people remembered the techniques that were used to sail them, and still practise the skills needed to build them This particular canoe, which is very big for modern times, was built on the tiny island of Ribono in Kiribati the islands that used to be called the Gilberts.
It is only about 50 feet long, enormous for today, but only half the size of the old canoes, and still the people are prepared to sail on journeys of up to 1,000 miles in it.
The techniques for building it are those that were used for the old canoes.
The lashings, for instance.
They are made from the fibres of coconut husks.
Clumps are teased out, rolled and twisted so that each fibre binds with its neighbours.
It is a repetitious job, but a skilled one if the string is going to be strong, and it is taken on by the women and the old people.
Hundreds of yards will be needed to build a big canoe.
It's used not only for lashing one spar to another but for sewing together the planks that form the sides of the big canoes.
The Pandanus tree produces strap-like leaves, which, when dried and split, provide ribbons that are woven into strong and durable mats to serve as sails.
So if you have the necessary knowledge and skill, even a small atoll can provide all the materials to build an ocean-going canoe.
In such craft, the Polynesians travelled right across the Pacific.
For a long time, Europeans, so proud of their navigating skills, maintained that the Polynesian voyages were accidental, made when fishing canoes were blown off course.
But the huge canoes carried women and children, and were loaded with plants and animals, with every intention of founding new colonies.
The Polynesian navigators had and have the most astonishing powers of observation by which they find their way.
A particular kind of bird during one season of the year will always travel in a certain direction.
Some birds are ocean-goers, others seldom travel far from their nesting grounds, so spotting one can indicate that there's land close by, and following it may take you there.
Distant islands can be detected by their effect on the ripples on the surface of the sea.
Tall islands trail clouds of characteristic shape like smoke from a chimney blown by the wind, and since they are so high in the sky, they can be recognised and identified long before the island is visible.
Using such techniques and observing the sun and stars, the pattern of the winds, and feeling through the rudder the movements of swells and currents, the Polynesians colonised island after island.
Their original home was in the western Pacific.
They reached the Tahitian islands, in the centre of the ocean, over 2,000 years ago.
They sailed so far eastward that they reached Easter Island, three-quarters of the way to the coast of South America.
Those that settled here seem to have been more isolated than most, and, like so many other islanders, they developed their own culture.
They carved the rocks of their headlands into strange shapes.
On the flanks of the great volcano that built their island, they set up huge images whose enigmatic faces have haunted the European imagination ever since they were discovered by westerners two centuries ago.
The heyday of the Easter Island culture seems to have been passed long before Europeans arrived, for many statues were overturned and some lay half-finished and abandoned where they had been carved in the quarries.
The scale of these Polynesian voyages is difficult to imagine.
From their headquarters in Samoa to their most northerly colony in Hawaii, which they reached by way of the Marquesas, was some 5,000 miles.
The journey to Easter Island, about 3,300 miles.
But the most extraordinary voyage of all took them across 4,000 miles of open ocean, south to New Zealand.
The group that landed here, ancestors of the Maori, arrived about 1,500 years ago.
The land they discovered must have been a great surprise to them, for it was very different from the tropical island from which they had come.
For much of the year, it was bitterly cold.
In the South Island stood great mountain ranges covered with snow and ice that the Maori can never have seen before.
Not only that, but the forests were far richer in animals and plants than any island they had yet discovered.
That was because these islands had a very different origin and history.
They were neither flat coral atolls nor were they the tips of volcanoes that had risen above the surface of the Pacific in comparatively recent geological time.
These islands of New Zealand were ancient lands.
Fragments of a great supercontinent of which Australia, Antarctica and South America had been a part.
In consequence, they had on them many more different kinds of animals than other more recent islands.
They had animals like this.
This is the tuatara.
It's a reptile, it's nocturnal and solitary, and it's a flesh-eater.
It feeds on insects, earthworms and even young nestling birds.
It might look like a lizard, but it's a more ancient creature than that, more closely related to the early dinosaurs than it is to the modern family of lizards.
Once creatures like it must have swarmed over that great supercontinent, but New Zealand split away from the supercontinent before the great expansion of the early mammals which ultimately led to the extinction of most of the early reptiles.
Only in New Zealand did the tuatara remain safe.
And New Zealand also has been a sanctuary for another early creature.
The kiwi.
It's a bird, but what an odd one.
It has no visible wings and no tail and lives in a burrow.
There, it produces a single and enormous egg.
Flightless, living in burrows, with feathers so long and loose they look like shaggy fur, and running quietly across the forest floor at night in search of food, this odd animal could be considered a kind of bird equivalent of a mammal.
Indeed, the kiwi does play that role in these islands where originally there were no land mammals of any kind.
It has, however, retained that characteristic possession of the bird, a beak and it uses it to collect worms, plunging it deep into the earth to smell for them as a mammal does.
The ancestors of the kiwi were flightless before New Zealand was isolated, for the kiwi is a ratite.
Other members of that family of ancient flightless birds still survive on other fragments of the great supercontinent.
There's the ostrich in Africa, the rhea in South America and the emu in Australia.
All those are bigger than the kiwi, but the kiwi once had a cousin living here in New Zealand that was bigger than the lot of them.
It was probably the tallest bird that has ever existed, the moa.
Its bones have been found in great numbers here in New Zealand.
Often in between the ribs have been found piles of polished pebbles.
They were the stones from the gizzard with which the moa ground up its food, and from the vegetable remains, we know that it ate fruit, twigs and the leaves of trees.
There were a dozen or so different species of moa of varying sizes.
This particular one was the biggest of all.
It was not the heaviest bird that has ever lived, its relative, the extinct elephant bird that lived in Madagascar was that, but its weight nonetheless was substantial, about 520 pounds, and it was the tallest of all birds, standing over 13 feet high.
In fact, it was the bird equivalent of a giraffe.
This is the mummified head and neck of one of the smaller species of moa, and it suggests, because many necks have been found attached to heads, that the Maori had so much moa meat that they could afford to throw away sections like this.
The Maori not only reduced the number of moa by hunting, they also burnt down the forests on which the moas depended.
And so, by the time the Europeans arrived here in the 18th century, the last of the moas had been extinct for some 200 years.
But in the millions of years that have passed since New Zealand was isolated as islands, many more modern creatures have arrived here.
They've got here, as they've managed to get to islands all over the world, by flying.
Some have changed only a little since they arrived.
The kereru is still quite clearly a kind of pigeon And this, the kea, is still recognisably a parrot.
Its ancestors came, doubtless, from that great parrot homeland, Australia, 1,000 miles away.
Since it's been here, it's probably changed its habits a good deal, for it's taken up life in the cold, high mountains where it feeds on berries and roots, buds and insects.
It has also, with that adaptability of diet characteristic of islanders, become a general scavenger, and will even feed on carrion like a crow or small vulture.
One parrot, here, however, has been changed extremely by island life.
The kakapo.
There are no ground-living leaf-eating mammals on the island, so this has become a kind of parrot-equivalent of a rabbit.
It's extremely nervous, nocturnal, and it lives on vegetation, but it shows those two characteristics of island-living creatures.
It has lost its powers of flight, so its only defence is to freeze motionless as it's doing now.
And secondly, it's a giant.
It's the biggest of all the parrots by weight.
A big one can weigh over three kilos.
It also shows only too vividly a third characteristic of island-living forms: Their extreme vulnerability.
When their islands are invaded by outsiders, they often have no defence.
The kakapo's troubles started when the Polynesians first came to New Zealand.
They brought a kind of rat which may have preyed upon the nestling kakapo, and the Polynesians themselves hunted it.
The real catastrophe came when Europeans arrived, because they brought with them those two merciless killers, the stoat and the cat Against them, the kakapo had no defence whatever.
Very rapidly, its numbers diminished until today there are not more than 60 individual kakapo left.
To give them some chance of survival, they've been taken to a small offshore island that has been cleared of cats.
Elsewhere, these domestic pets that were brought here to catch mice in houses have run wild in the forests, and prey on native birds which have not acquired the right reflexes to save themselves from its attacks.
Cats are not the only foreign killers here.
Ferrets were imported for hunting introduced rabbits.
They are domesticated polecats.
Some escaped, reverted to their wild state and bred.
This one is feeding on a penguin chick which must have been an easy victim.
None of New Zealand's flightless birds are safe from them.
People also introduced plant-eating animals.
Possums were brought from Australia as pets.
Rabbits were also imported to provide meat and fur, and to put to good use, as the importers must have thought, the abundant grass that was going to waste.
And red deer were released in the mountains to provide hunters with sport.
Yet these seemingly harmless vegetarians had a catastrophic effect on the native animals.
They grazed so effectively that they destroyed the trees and bushes.
The soil was washed away and the forest devastated.
Creatures were robbed of their cover and vegetation.
The problems of halting this destruction are very great.
This extraordinary bird is the takahe.
Like the kakapo, it epitomises the effects of island-living.
It's become a giant, for it's a rail, like the one in Aldabra, and the biggest of its family.
It's unique to these islands, it's flightless, and has virtually no defence against invaders.
At the beginning of this century, it was thought to be extinct.
Then, after no one had seen a living takahe for over 50 years, a small population was discovered in a remote valley in South Island.
There are about 200 left.
They are unlikely to spread, for their habitat elsewhere has been destroyed, and there is the greatest difficulty in getting them to breed in captivity.
So, unless man is prepared to change his attitude and become an active protector as he has done here in New Zealand, those strange specialised islanders are doomed to the fate of the first island-living creature that man exterminated and become as dead as the dodo.
Of course, not all the creatures that you find on islands necessarily spend all their time there.
Some like those tough international travellers over there, the gannets, just come here for lodging.
They, like the frigates and the boobies of Aldabra, the noddies and the terns of a thousand tropical atolls, find their food, not on the islands where they come to nest, but in the surrounding seas, and that is the vast and complex community that we'll be looking at next time.
They're miniature enclosed worlds where animals and plants become transformed into new species with extraordinary speed.
If you wanted to pick a really remote desert islan cut off from the rest of the world, you might well choose this one.
This is Aldabra in the Indian Ocean.
The nearest land in that direction is the coast of Africa, about 250 miles away.
Over there, about the same distance, is Madagascar, and if you sailed in that direction, you wouldn't hit much until you got to the coast of Australia 4,000 miles away.
The island is the tip of an extinct submarine volcano that rises 15,000 feet from the bottom of the Indian Ocean and is capped with coral rock.
When it finally rose above the surface of the sea about 50,000 years ago, it was lifeless, but now, a mere 50,000 years later, well, just look.
Frigate birds, thousands of them, circle above one end of the island.
They've come from all over the Indian Ocean, even from India itself 2,000 miles away, to nest on this particular island in the mangroves.
The white-headed birds among them are immatures, and there are two different species of them, one bigger than the other.
The males inflate their scarlet throat pouches to show that the site is taken, and to attract the female.
When she arrives, he persuades her to stay with ecstatic shakes of his head.
Red-footed boobies are here, too.
They're great travellers, and their chicks, which are already fledging, may well be fishing 3,000 or 4,000 miles away within a year.
Noddies nest not on Aldabra but on a neighbouring atoll, building platforms of seaweed in the Pisonia trees, and beneath, on the open coral sand, two million sooty terns lay their eggs.
Their vast numbers are an indication of the richness of the surrounding sea.
Every day, the birds take from it many tons of small fish, little squid and other marine creatures.
The atoll itself provides no food for them.
All a pair of sooty terns seek from it are a few square inches of dry land on which to place their single egg, and an absence of cats, rats and all other egg-stealers and chick-eaters that plague nesting sites on the mainland.
Such security is important to these terns, for not only do they lay their eggs exposed and unprotected on the ground, but their young remain flightless for several weeks after hatching and a hungry cat could cause havoc among them.
So terns find it well worthwhile, for the sake of such security, to fly hundreds of miles to this island.
The plants that grow on remote islands like Aldabra how do they get here? Well, some certainly come by sea.
In a short walk along this high-water mark, I've picked up already three different kinds of seeds.
Here's the biggest floating seed of them all.
This is a coconut.
There's the familiar nut which contains the white flesh, and this husk, from which we sometimes make coconut mats, is the flotation device.
Nuts like this can float in the sea for up to four months.
This one is dead but here is one that's alive and still sprouting The green stem springing from the top, a white rootlet striking down underneath.
Under natural conditions, coconuts establish themselves at the head of the beach.
As they grow taller, they lean out over the sand so that when they're full-grown, their nuts will drop within reach of the high tide and be washed out to sea to spread to other islands.
A land-living animal also reached here by sea.
The time and place to find it is at night among the coconut groves.
It travelled here as a larva in the same way as the coconuts, floating in the surface waters.
One or two in a million were washed up on the beach and crawled ashore to live on land among the coconuts, feeding on them.
It's almost the only creature here likely to give you a painful bite, so it needs tackling with care.
It's the coconut crab.
Its legs are so long that it can embrace the trunk of a coconut palm, and it has no difficulty in clambering up to the top.
There it cuts down young nuts with its pincers, and returns to the ground to feed on the soft white coconut flesh.
Crabs as a group are sea-living creatures and breathe in water by means of gills.
To breathe in air, the coconut crab has developed large pouches within its shell that have moist linings and can act as simple lungs.
But when it breeds, it has to return to the sea.
There it releases its eggs and sperm into the water at high tide, so that its larvae will circulate through the sea, and may be washed up on some new island.
One exceptional land animal made the voyage to Aldabra as an adult: Its most famous inhabitant, the giant tortoise.
Most tortoises are naturally buoyant.
If one on the coast of mainland Africa, grazing among the mangroves, were swept out to sea, it might survive long enough to be carried by currents to the islands of the Indian Ocean, and later to spread among them.
That, almost certainly, is how ancestors of the Aldabran giant tortoise reached here.
It's not a very hospitable place for animals like tortoises that feed on land-living plants.
The coral rock which forms the substance of the island erodes into a honeycomb of wickedly sharp blades and spikes.
Any creature moving over it has to step with care if it's not to cut itself badly.
Here and there, the rock forms deep pits into which tortoises sometimes tumble.
When that happens, there is no escape, and the trapped animals, even if they survive the fall, die from starvation Quite apart from such traps, the island is a harsh, taxing place in which to live.
The tropical sun, beating down on the animals, threatens to bake them alive inside their shells, and the remains of casualties are common.
So as the day heats up, the tortoises head determinedly for the few trees that can provide shade.
Here and there on some beaches grow low, windswept Guettarda trees.
By noon, the ground beneath their branches is packed with refugees from the sun, waiting for the temperature to fall so that they can search for edible leaves.
Birds, too, can overheat.
The frigates swoop over the one almost permanent lagoon of rainwater on the island, snatching sips from its surface.
Tortoises, too, must have fresh water.
Although they don't drink every day, they must do every week or so if they're to survive.
Water can also cool an overheated body.
As the dry season progresses, the water evaporates and the pools get smaller and more crowded.
Many that came here for relief are near the end of their strength.
Some are unable to drag themselves out of the mud, and so die of starvation.
And yet, in spite of all these hardships, the tortoises breed and proliferate.
There are some 150,000 of them on the atoll.
Their staple food is vegetation and they crop the grass right down to the rootstock.
But as island animals everywhere tend to do, they've broadened their taste in food to include almost anything that is edible, including the carcasses of their dead companions.
Flesh is too nutritious to be allowed to rot and go to waste in this land where there is so little to eat.
50,000 years, which is the time, apparently, that Aldabra has been above the sea, is not a very long time in terms of evolution.
Nonetheless, 50,000 years of isolation on the island has brought changes to many plants and animals that live here.
They've begun to take on their own character, so now they differ slightly both from the ancestors which colonised the island and from their nearest relations elsewhere in the world.
For example, this close-cropped withered turf around me contains about 20 different species of plants.
All have been relentlessly cropped by giant tortoises like that.
And look, for example, at this little sedge.
Most sedges bear their flowers at the top of stems that rise quite high above the leaves.
Flowers sticking up like this would not survive long on Aldabra.
The tortoises would eat them.
These Aldabran sedges bear their flowers and develop their seeds close to the rootstock where the jaws of the hungry tortoises can't reach them.
The changes that take place in an island species are not always directly useful like that.
Another of Aldabra's plants has changed in a way that seems to have no practical significance at all.
This is a lily called Lomatophyllum.
It's slightly different in colour from Lomatophyll growing elsewhere, but that's all.
The difference is very trivial.
But some island plants are spectacularly different from their nearest relatives.
Very, very rarely, extraordinary double nuts like this are washed up on the shores of the coral islands of the Indian Ocean.
For centuries, nobody knew where they came from.
Some said they were produced by fantastic palm trees that grew under the surface of the sea, so they were called coco-de-mer.
People believed that their kernels could be made into irresistible love potions and that their shells, when turned into a cup, would render the most powerful poison harmless.
A single nut like this was literally worth a king's ransom.
It wasn't until the 18th century that people discovered that the palms that produced these nuts grew in one tiny group of islands in the Seychelles, some 700 miles from Aldabra.
The largest surviving group of these trees stands on the little island of Praslin.
There are male and female trees.
The males produce small yellow flowers on long spikes, and on them lives a little gecko, feeding on their nectar and pollen.
Once again, it's an island original, slightly different in colour from others in neighbouring islands.
The female flowers start as small reddish buds, no bigger than a man's fist, but they will develop into the biggest seed produced by any plant.
It takes seven years for the nuts to develop, and when they are mature, they are so large and so heavy that almost the only way of opening them is with a saw.
Inside, you can see how very different they are from coconuts.
Not only do they have two lobes to them, but the nut itself is full solid with flesh.
Flesh that is so heavy that these mature nuts won't float in sea water.
Indeed, sea water kills them.
And that means two things.
First of all, that these palms have never been able to spread to other islands, and secondly, that they must have actually evolved here.
Isolation changes not only plants but animals.
On Aldabra, wandering among the tortoises are sacred ibis with light blue eyes.
Others elsewhere have dark eyes.
The Aldabran ibis breed among themselves and feed on small shore creatures.
Land crabs are far too big to be eaten, but they have to be pecked to clear them out of the way.
Several species of Aldabran birds have developed slight variations that make them unique.
The kestrel here is slightly smaller than the Madagascar species, but otherwise the same.
The Aldabran sunbird, however, is a little darker than its African relations.
But perhaps the most dramatic and certainly the most endearing quality brought to some of the birds of Aldabra by isolation is this.
Not only extreme tameness, but flightlessness.
This is the Aldabran rail.
Flying takes a lot of energy.
It's of obvious value when escaping ground-living enemies, but there are no such enemies on Aldabra or other remote islands.
So some birds that reach such islands by air have given up flying.
Their wing muscles have dwindled and they can't fly even if they wanted to.
The Aldabran rail is only one example.
A kind of pigeon once lived on another island in the Indian Ocean: Mauritius.
It, too, became flightless and grew as big as a turkey.
It was so tame that European sailors were able to kill it with clubs.
They called it the dodo, and in less than 200 years after finding it, they'd exterminated it.
Grazing alongside the dodo in Mauritius, and living in other islands in the Indian Ocean as well, were giant tortoises.
They, too, were taken for food by seamen and were exterminated.
But Aldabra is so remote that few ships come near it, and here alone, the tortoises have survived.
It seems likely that the African ancestors of these creatures were of a normal size, and that these tortoises became giants as a consequence of living on islands.
Isolation may have had another effect on the tortoises as well.
When African tortoises are threatened, they behave in the same way as this baby Aldabran tortoise.
They first pull in their head, and then they pull after it their heavily armoured front legs so that nothing sticks out and they're comparatively safe from their enemies.
But when the Aldabran tortoise grows up, its proportions change, as this one's have done.
This one is now so big that these huge legs won't fit into this space, so that whatever it does, something sticks out.
It's a fair bet that if there was a hyena on the island, it would make a meal of the giant tortoise.
But there isn't on Aldabra, so this creature's saf Just why the island tortoises should have grown so huge, and another species has done the same in the Galapagos islands, is by no means clear.
It may be that a large animal with big reserves of fat is better able to survive bad seasons when there's little to eat.
It may even be that with no predators on the island, these long-lived creatures just go on growing, but it is not a phenomenon that is restricted to tortoises.
On an island 3,000 miles away from Aldabra, there is another giant reptile.
Komodo is a small island in Indonesia.
From here, back in the 1920s, came stories of a huge lizard that became known as the Komodo dragon, and here the dragons still live.
It's not difficult to find them.
All you need is the carcass of a goat, preferably decayed and smelly, and the scent will attract them from miles around.
It used to be thought that these very big ones were entirely scavengers, relying on what carrion they could find, but now we know that actually they are active killers.
They attack and kill goats, young buffalo, and even on occasion, man.
The reason that I can stand here with relative safety is that their eyesight is not very good, they are almost deaf, and they rely on their senses, primarily on that big yellow tongue which flicks out and tastes the air.
So with any luck, the smell of these dead goats is more powerful than mine, so they will take no notice of me.
They are, in fact, the kings of their island.
They are the top predator.
There is nothing here which preys upon them and is bigger, and nothing with which they have to share their food.
So, from that point of view, there is no reason why they shouldn't grow big.
And the fact is that there is a positive advantage in growing big, because the big ones are getting the bigger share of the food.
Not only that, but we now know that these big ones eat small ones.
That perhaps is a reason why, in the isolation of their island, these kings of Komodo have grown so huge.
And they are indeed immense.
They're related to the water monitors of Asia and Africa and the goannas of Australia, but they are much more massive, for whereas two-thirds of the length of these other monitors is taken up by a long thin tail, the dragon's tail is only about half its length.
Big ones like this can weigh up to 100 pounds and grow to over nine feet long.
Komodo is not, like Aldabra, a coral atoll growing on the drowned tip of a submarine volcano, but the eroded remains of one that stood many thousands of feet above sea level.
Volcanoes, indeed, have built many of the most isolated islands.
The Hawaiian islands, lying in the eastern Pacific, are all volcanic, and the biggest and newest of them is still erupting.
Torrents of basaltic lava erupting from vents 10,000 feet up on the mountain sometimes flow for many miles down the volcano's flanks.
When, eventually, they cool and solidify, they become vast slopes of black naked rock.
Such areas as this may remain virtually sterile for decades.
Some vents produce vast quantities of granular ash which builds up around them into cones.
Plants have a better chance of getting root on such material, and within a century or so, the ash slopes may be covered with green.
These high islands collect moisture-laden clouds, and on the windward side, rain falls very heavily indeed.
Streams flowing down the mountainside cut through the layers of loosely compacted ash, eroding deep valleys.
So, unlike a coral atoll, which is a plain platform of coral, sand and rock only a few feet high, these immense volcanic islands of Hawaii offered their colonists a great variety of habitat from high cold slopes of ash on the summits to well-watered valleys, hot, lush and humid, near sea level, from new, naked basalt to long-established forest growing on ancient lava flows.
To exploit them, the animal colonists changed not into just one new form, but into a multitude.
This bird, the palila, is one of a large family of closely related Hawaiian birds, the honeycreepers.
Their ancestors were probably finch-like birds that were swept here, perhaps by a freak storm many thousands of years ago.
Once here, they developed into over 30 different species, each with its own diet and habitat.
The palila lives largely on seeds and has the short, powerful beak needed to open and crack them.
The 'amakihi, while there's no doubt that it and the palila are related, has a slender beak, suited to picking up small insects and sipping nectar from shallow flowers.
Some species have developed striking feather colours and adornments.
These enable the male and female to identify one another so they don't interbreed with near cousins, and the species becomes increasingly distinct.
So the 'apapane not only has a longer beak to suit its almost exclusive diet of nectar, but a conspicuous red head.
The 'akohekohe lives on a mixed diet of insects and nectar, and has developed a little crest of white feathers at the base of its beak.
The 'i'iwi is scarlet and has a particularly long curved bill that allows it to probe deep into trumpet-shaped flowers such as giant lobelias and bananas.
And perhaps most engaging of all, the akiapolaau, with a splendid dual-purpose beak, the lower mandible pick-like to chip away bark to find insects, and an upper mandible elongated into a probe with which to winkle them out.
It's located a beetle larva burrowing away within the bark.
Look how dexterously it uses the two halves of its beak for these different purposes.
The situation amongst Hawaii's insects is even more extreme than it is among its birds.
There is a kind of fly called Drosophila.
It's found in many parts of the world.
In North America, for example, there are about 200 species, but in these tiny islands of Hawaii, there are at least 800.
It seems that soon after the islands' formation, one or at most two species of Drosophila reached the islands, and they found the same situation as the honeycreepers found, a lot of vacant niches.
And so they evolved to fill them, and they are now Drosophila, the larvae of which feed on fruit or rotting leaves or fungi, or bark or even spiders' eggs.
But now the situation becomes more complex because in Hawaii, there are lava flows like this, and such lava flows often isolate patches of ancient forest like that over there, and in one small patch of forest, there may well be one particular species of Drosophila that occurs nowhere else.
And there are some just there.
These particular ones belong to a group which have evolved, in their isolation, an extraordinary courtship behaviour, just as some honeycreepers have evolved bright colours.
It's an insect equivalent of the arena display of antelope.
The males maintain tiny territories and display and battle with one another.
Instead of antlers, they've developed heads shaped like mallets.
In another species, the male courts the female by hoisting his abdomen over his back and showering her with an aphrodisiac perfume.
Isolation has also affected the wings of Hawaiian insects.
Flying on an island is dangerous.
It risks being blown out to sea, and this extraordinary bug never takes to the air.
Its wings are tiny, and used only for flirting in courtship.
This lacewing can't even use them for that.
Its wings have become fused together to form a shell.
The Hawaiian cranefly has lost its wings completely.
This cranefly's taste for fruit is typical of its family, but other insects have changed their feeding habits.
This flightless bug has adopted the hunting techniques of the mantis which never naturally reached the island.
And this fly is going to get a shock.
The twig caterpillar doesn't, like most twig caterpillars elsewhere, feed on leaves, but has become a carnivore.
It detected the fly with tiny hairs on its back en They trigger the caterpillar to arch backwards and pounce on whatever touched it.
So isolation, by restricting the kinds of creature that reached Hawaii, allows those that did great freedom to develop into different and unexpected forms.
Human beings, the Polynesians, reached Hawaii several thousand years ago.
When Europeans arrived, they found to their surprise an unknown people with an elaborate and splendid culture.
The Hawaiians were superb seamen.
They not only paddled dugout canoes, but sailed immense ocean-going double canoes that could carry several hundred passengers, and that tradition survives still in many parts of the Pacific.
The last of the really big canoes must have disappeared about 100 years ago, but still, in the remoter parts of the Pacific, people remembered the techniques that were used to sail them, and still practise the skills needed to build them This particular canoe, which is very big for modern times, was built on the tiny island of Ribono in Kiribati the islands that used to be called the Gilberts.
It is only about 50 feet long, enormous for today, but only half the size of the old canoes, and still the people are prepared to sail on journeys of up to 1,000 miles in it.
The techniques for building it are those that were used for the old canoes.
The lashings, for instance.
They are made from the fibres of coconut husks.
Clumps are teased out, rolled and twisted so that each fibre binds with its neighbours.
It is a repetitious job, but a skilled one if the string is going to be strong, and it is taken on by the women and the old people.
Hundreds of yards will be needed to build a big canoe.
It's used not only for lashing one spar to another but for sewing together the planks that form the sides of the big canoes.
The Pandanus tree produces strap-like leaves, which, when dried and split, provide ribbons that are woven into strong and durable mats to serve as sails.
So if you have the necessary knowledge and skill, even a small atoll can provide all the materials to build an ocean-going canoe.
In such craft, the Polynesians travelled right across the Pacific.
For a long time, Europeans, so proud of their navigating skills, maintained that the Polynesian voyages were accidental, made when fishing canoes were blown off course.
But the huge canoes carried women and children, and were loaded with plants and animals, with every intention of founding new colonies.
The Polynesian navigators had and have the most astonishing powers of observation by which they find their way.
A particular kind of bird during one season of the year will always travel in a certain direction.
Some birds are ocean-goers, others seldom travel far from their nesting grounds, so spotting one can indicate that there's land close by, and following it may take you there.
Distant islands can be detected by their effect on the ripples on the surface of the sea.
Tall islands trail clouds of characteristic shape like smoke from a chimney blown by the wind, and since they are so high in the sky, they can be recognised and identified long before the island is visible.
Using such techniques and observing the sun and stars, the pattern of the winds, and feeling through the rudder the movements of swells and currents, the Polynesians colonised island after island.
Their original home was in the western Pacific.
They reached the Tahitian islands, in the centre of the ocean, over 2,000 years ago.
They sailed so far eastward that they reached Easter Island, three-quarters of the way to the coast of South America.
Those that settled here seem to have been more isolated than most, and, like so many other islanders, they developed their own culture.
They carved the rocks of their headlands into strange shapes.
On the flanks of the great volcano that built their island, they set up huge images whose enigmatic faces have haunted the European imagination ever since they were discovered by westerners two centuries ago.
The heyday of the Easter Island culture seems to have been passed long before Europeans arrived, for many statues were overturned and some lay half-finished and abandoned where they had been carved in the quarries.
The scale of these Polynesian voyages is difficult to imagine.
From their headquarters in Samoa to their most northerly colony in Hawaii, which they reached by way of the Marquesas, was some 5,000 miles.
The journey to Easter Island, about 3,300 miles.
But the most extraordinary voyage of all took them across 4,000 miles of open ocean, south to New Zealand.
The group that landed here, ancestors of the Maori, arrived about 1,500 years ago.
The land they discovered must have been a great surprise to them, for it was very different from the tropical island from which they had come.
For much of the year, it was bitterly cold.
In the South Island stood great mountain ranges covered with snow and ice that the Maori can never have seen before.
Not only that, but the forests were far richer in animals and plants than any island they had yet discovered.
That was because these islands had a very different origin and history.
They were neither flat coral atolls nor were they the tips of volcanoes that had risen above the surface of the Pacific in comparatively recent geological time.
These islands of New Zealand were ancient lands.
Fragments of a great supercontinent of which Australia, Antarctica and South America had been a part.
In consequence, they had on them many more different kinds of animals than other more recent islands.
They had animals like this.
This is the tuatara.
It's a reptile, it's nocturnal and solitary, and it's a flesh-eater.
It feeds on insects, earthworms and even young nestling birds.
It might look like a lizard, but it's a more ancient creature than that, more closely related to the early dinosaurs than it is to the modern family of lizards.
Once creatures like it must have swarmed over that great supercontinent, but New Zealand split away from the supercontinent before the great expansion of the early mammals which ultimately led to the extinction of most of the early reptiles.
Only in New Zealand did the tuatara remain safe.
And New Zealand also has been a sanctuary for another early creature.
The kiwi.
It's a bird, but what an odd one.
It has no visible wings and no tail and lives in a burrow.
There, it produces a single and enormous egg.
Flightless, living in burrows, with feathers so long and loose they look like shaggy fur, and running quietly across the forest floor at night in search of food, this odd animal could be considered a kind of bird equivalent of a mammal.
Indeed, the kiwi does play that role in these islands where originally there were no land mammals of any kind.
It has, however, retained that characteristic possession of the bird, a beak and it uses it to collect worms, plunging it deep into the earth to smell for them as a mammal does.
The ancestors of the kiwi were flightless before New Zealand was isolated, for the kiwi is a ratite.
Other members of that family of ancient flightless birds still survive on other fragments of the great supercontinent.
There's the ostrich in Africa, the rhea in South America and the emu in Australia.
All those are bigger than the kiwi, but the kiwi once had a cousin living here in New Zealand that was bigger than the lot of them.
It was probably the tallest bird that has ever existed, the moa.
Its bones have been found in great numbers here in New Zealand.
Often in between the ribs have been found piles of polished pebbles.
They were the stones from the gizzard with which the moa ground up its food, and from the vegetable remains, we know that it ate fruit, twigs and the leaves of trees.
There were a dozen or so different species of moa of varying sizes.
This particular one was the biggest of all.
It was not the heaviest bird that has ever lived, its relative, the extinct elephant bird that lived in Madagascar was that, but its weight nonetheless was substantial, about 520 pounds, and it was the tallest of all birds, standing over 13 feet high.
In fact, it was the bird equivalent of a giraffe.
This is the mummified head and neck of one of the smaller species of moa, and it suggests, because many necks have been found attached to heads, that the Maori had so much moa meat that they could afford to throw away sections like this.
The Maori not only reduced the number of moa by hunting, they also burnt down the forests on which the moas depended.
And so, by the time the Europeans arrived here in the 18th century, the last of the moas had been extinct for some 200 years.
But in the millions of years that have passed since New Zealand was isolated as islands, many more modern creatures have arrived here.
They've got here, as they've managed to get to islands all over the world, by flying.
Some have changed only a little since they arrived.
The kereru is still quite clearly a kind of pigeon And this, the kea, is still recognisably a parrot.
Its ancestors came, doubtless, from that great parrot homeland, Australia, 1,000 miles away.
Since it's been here, it's probably changed its habits a good deal, for it's taken up life in the cold, high mountains where it feeds on berries and roots, buds and insects.
It has also, with that adaptability of diet characteristic of islanders, become a general scavenger, and will even feed on carrion like a crow or small vulture.
One parrot, here, however, has been changed extremely by island life.
The kakapo.
There are no ground-living leaf-eating mammals on the island, so this has become a kind of parrot-equivalent of a rabbit.
It's extremely nervous, nocturnal, and it lives on vegetation, but it shows those two characteristics of island-living creatures.
It has lost its powers of flight, so its only defence is to freeze motionless as it's doing now.
And secondly, it's a giant.
It's the biggest of all the parrots by weight.
A big one can weigh over three kilos.
It also shows only too vividly a third characteristic of island-living forms: Their extreme vulnerability.
When their islands are invaded by outsiders, they often have no defence.
The kakapo's troubles started when the Polynesians first came to New Zealand.
They brought a kind of rat which may have preyed upon the nestling kakapo, and the Polynesians themselves hunted it.
The real catastrophe came when Europeans arrived, because they brought with them those two merciless killers, the stoat and the cat Against them, the kakapo had no defence whatever.
Very rapidly, its numbers diminished until today there are not more than 60 individual kakapo left.
To give them some chance of survival, they've been taken to a small offshore island that has been cleared of cats.
Elsewhere, these domestic pets that were brought here to catch mice in houses have run wild in the forests, and prey on native birds which have not acquired the right reflexes to save themselves from its attacks.
Cats are not the only foreign killers here.
Ferrets were imported for hunting introduced rabbits.
They are domesticated polecats.
Some escaped, reverted to their wild state and bred.
This one is feeding on a penguin chick which must have been an easy victim.
None of New Zealand's flightless birds are safe from them.
People also introduced plant-eating animals.
Possums were brought from Australia as pets.
Rabbits were also imported to provide meat and fur, and to put to good use, as the importers must have thought, the abundant grass that was going to waste.
And red deer were released in the mountains to provide hunters with sport.
Yet these seemingly harmless vegetarians had a catastrophic effect on the native animals.
They grazed so effectively that they destroyed the trees and bushes.
The soil was washed away and the forest devastated.
Creatures were robbed of their cover and vegetation.
The problems of halting this destruction are very great.
This extraordinary bird is the takahe.
Like the kakapo, it epitomises the effects of island-living.
It's become a giant, for it's a rail, like the one in Aldabra, and the biggest of its family.
It's unique to these islands, it's flightless, and has virtually no defence against invaders.
At the beginning of this century, it was thought to be extinct.
Then, after no one had seen a living takahe for over 50 years, a small population was discovered in a remote valley in South Island.
There are about 200 left.
They are unlikely to spread, for their habitat elsewhere has been destroyed, and there is the greatest difficulty in getting them to breed in captivity.
So, unless man is prepared to change his attitude and become an active protector as he has done here in New Zealand, those strange specialised islanders are doomed to the fate of the first island-living creature that man exterminated and become as dead as the dodo.
Of course, not all the creatures that you find on islands necessarily spend all their time there.
Some like those tough international travellers over there, the gannets, just come here for lodging.
They, like the frigates and the boobies of Aldabra, the noddies and the terns of a thousand tropical atolls, find their food, not on the islands where they come to nest, but in the surrounding seas, and that is the vast and complex community that we'll be looking at next time.