[waves roaring] [dramatic music] [bird squawking] [dramatic music] - These are the islands that caused a worldwide revolution in scientific thought.

This tiny group of volcanic islands, isolated, unimpressive, inhospitable, led man to a whole new idea about the very nature of life on earth.

In the fall of 1835, a 26-year-old English naturalist stepped onto the shores of the Galapagos Islands.

His name was Charles Darwin.

Hi, I'm George Page for Nature.

And the young Darwin was not impressed with his first views of the Galapagos Islands.

In his famous journal, "The Voyage of the Beagle", he wrote, "Nothing could be less inviting "than the first appearance of the islands."

But as he came into contact with their extraordinary wildlife, he began to make observations which, eventually, would inspire one of the most profound revolutions in human thought, the theory of evolution.

He was struck by the strangeness of the islands' antediluvian beasts, as he called them, and found their peculiar tameness so charming that he couldn't resist riding on the backs of giant tortoises and pulling the tails of the iguanas.

After his return to England, Darwin slowly began to realize that each island in the isolated archipelago was home to closely related but markedly different varieties of wildlife.

Somehow, they had been modified to take advantage of the Galapagos varied habitats.

24 years later, he finally published his findings in this book, "On the Origin of Species", and the world has never been the same since.

Now, we followed Darwin to Galapagos since we began the first of three programs about the natural history and the bizarre creatures of these remarkable islands.

[dramatic music] The islands have been described as a cinder pile, 600 miles out in the Pacific Ocean.

The Galapagos consistent entirely of volcanic lava spewed out from the ocean bed.

Over the last two million years, some of the lava has broken down into soil, but, in places, it looks as though it flowed only yesterday.

[dramatic music] Much of the vegetation that has colonized the islands is as weird as the landscape.

This Brachycereus cactus is the first plant to grow in a recently-formed lava flow.

The lowland areas are completely arid.

This is where the Opuntia grows freely, a prickly pair species, which like so many of the other plants grows only in the Galapagos.

[birds and insects chirping] Then there's the Jasminocereus cactus.

[birds and insects chirping] There are greener areas, but you must climb to reach them.

On some of the largest islands, volcanoes rise to between three and 6,000 feet.

[bird screeching] Around the crater, condensing steam from fumaroles and the moisture from low clouds produce mosses, ferns and vegetation of tropical lushness.

[birds and insects chirping] [waves crashing] Much of the shoreline is uncompromisingly harsh.

The lava constantly pounded by the Pacific swell.

[waves roaring] [seal whimpering] The unique quality of the landscape, the flora and the fauna raises many fascinating questions.

How did the ancestors of the present Galapagos creatures get to these remote islands in the first place?

When did they arrive?

How did the islands themselves appear so recently in geological time?

Fortunately, that part of the puzzle is the easiest to solve.

The Galapagos belong to Ecuador and are situated on the equator.

Two geological features have produced the Galapagos.

First, they are close to the junction of three of the earth's moving plates, the Cocos, Pacific and Nazca plates.

Second, they lie over a volcanic hotspot where the molten rock pierces the plates.

The Nazca plate on which the islands sit is moving eastward at about three inches per year.

The active volcanic islands, such as Isabela and Fernandina, are still over the hotspot.

Those to the east have already moved away.

They are, therefore, older and colder.

About 20 million years from now, the Galapagos Islands will have moved with the Nazca plate until they finally disappear beneath the waves.

But by then, it's possible that the hotspot will have produced other islands to replace them.

[volcano roaring] This is what the volcanic process looks like when it happens on the seabed.

The emission of lava has been going on for more than 10 million years.

[volcano roaring] Gradually, the underwater lava built up a vast platform with large fissures through which it flowed.

The weird pillar formations are typical of lava floods on the ocean floor.

They're caused by columns of rapidly cooling molten rock.

Eventually, the plateau increased in extent and height.

Until about five million years ago, some volcanoes broke through the surface.

[volcano roaring] Sometimes, as in the case of the largest island, Isabela, several volcanoes emerged and, eventually, joined up to form one big island.

The process is continuing.

The Galapagos are one of the most active volcanic ocean areas on earth.

There are 13 main islands, four of them sparsely inhabited, and over 40 rocks and islets in the archipelago.

Isabela is 45 miles long and, in parts, 24 miles wide.

It has five still active large volcanoes, the tallest rising to almost 6,000 feet.

Most of the islands are less than two million years old, some less than a million.

Isabela is one of the younger ones.

[dramatic music] To the west of it, separated by a narrow straight called the Bolivar Channel, lies Fernandina with one highly active volcano.

Near the shore are some brackish lagoons and mangrove thickets.

Inland, much of Fernandina is composed of brittle lava, practically impossible to walk on.

Santa Cruz is an older island.

Its volcanic days are over.

The highlands in the background are a reminder of the past.

The second largest island is also headquarters of the Galapagos National Park and the Darwin Research Station.

Espanola, the most southerly island, was never a volcano.

It's a flat lump of lava about four miles long thrust up from the seabed.

This is where 20,000 pairs of waved albatrosses nest in two colonies.

It's one of the earliest islands, probably about four million years old.

[dramatic music] Floreana is an old island too.

It was the scene of much volcanic activity in the past and has more than 50 small cones, the largest rising to only 2,000 feet.

Islets and rocks are a common feature of the Galapagos.

This is Daphne Major with a crater that's a great attraction to nesting seabirds, especially blue-footed boobies.

[dramatic music] Different as they are in shape and size, all the islands share a common volcanic origin.

All are relatively young, between four and one million years old, and all the Galapagos Islands, great and small, are home to the most fascinating animal population on earth.

[dramatic music] Heading the cast, if only by virtue of sheer weight and size, are the giant tortoises, Galapagos in Spanish, after which the islands take their name.

[dramatic music] The males can weigh up to 600 pounds.

It's thought that they can live for up to 200 years, though, no one has yet been able to confirm this in the wild.

They have few natural predators, but these harmless vegetarians have suffered heavily at the hands of man and have been wiped out completely on some of the islands.

[dramatic music] Most of the surviving tortoises live in the moist, volcanic uplands because of the plentiful vegetation.

[bird screeching] Next are the two great lizards of the Galapagos.

The land iguanas are usually found in the dry areas, but, once a year, the largest concentration of all occurs on the crater rim of the great active volcano on the island of Fernandina.

The land iguanas come here to nest each year.

[wind roaring] There's never been a land bridge connecting the islands to south or central America.

So, only a few mammals, two bats and some rat species, have ever made the journey.

Reptiles apparently are better adapted to ocean travel.

To look at the marine iguana, you wouldn't think it had evolved from the same ancestor as the land iguana.

This one is in breeding colors.

It's the only marine lizard in the world feeding on algae on the lava rocks and below the surface.

[water gurgling] Of the seabirds, half are native species or a subspecies.

One of those unique to the islands is the Galapagos flightless cormorant.

The swallow-tailed gull, another unique species, is the only nocturnal gull in the world.

It's believed it adapted to feeding at night in order to escape the food-stealing attentions of the frigate birds.

The large eye is typical of a nocturnal creature.

The swallow-tailed gull is so unlike all other gulls that it's placed in a genus of its own.

[bird crying] The other gull species found only in the Galapagos is the lava gull.

Although, it does have a close relative on the mainland, the laughing gull.

The gray lava coloring enables it to merge with its background.

[bird cooing] The Galapagos hawk has obvious buzzard hawk ancestors on the mainland, but it too is a separate Galapagos species.

It's a fierce and successful predator preying on small birds, lava lizards and young iguanas.

[bird screeching] Along with the tortoises, iguanas and its famous finches, the Galapagos mockingbirds gave Charles Darwin pointers for his series on evolution.

Quite different from mainland mockingbirds, they have evolved into four separate species.

They're opportunistic feeders and scavengers and can be fiercely predatory.

The victims here are newly-hatched turtles.

Of the seabirds that chose the islands as their only breeding ground, the waved albatross is the most impressive.

[water gurgling] As if the Galapagos bird list wasn't strange enough, it includes a penguin.

The Galapagos penguin is one of the smallest and, certainly, the most northerly of all penguin species.

It's restricted to only the coldest waters of the island.

[penguin screeching] Like the penguin, fur seals are normally found in cold even sub-Antarctic seas.

They too are sufficiently different from their nearest relatives to be given the status of a separate species.

[sea lion bellowing] [waves roaring] The sea lions lack the dense undercoat of the fur seals.

They differ from their sea lion ancestors in California, mainly in size.

They're slightly smaller and are a Galapagos subspecies.

[water splashing] The 13 species of finches, often called Darwin's finches, form the evolutionary showpiece of the archipelago.

Small, rather uninteresting looking birds, they have descended from one common mainland ancestor.

The most amazing of all is the woodpecker finch, which uses a stick or cactus spine to pry insects out of dead trees and, thus, becomes one of nature's few tool-using animals [birds chirping] Once the islands had appeared, how did the ancestors of the present unique Galapagos species reach them?

Well, there's no doubt that the sea lions came south from California.

The fur seals and penguins came from the opposite direction led by the cold Peru current.

The route taken by tortoises, iguanas and finches is less certain.

Some experts named South America as their starting point, but, today, many scientists think that central America in the region of Panama is more likely.

The finches were probably blown here by storms.

Tortoises and iguanas may either have floated or arrived on natural rafts.

[insects chirping] The riverside forest of Panama were probably the original home of the ancestors of the Galapagos reptiles.

[insects chirping] No one can be quite certain, but this is now thought to be the creature from which the two very different species of Galapagos iguanas evolved.

It's the green iguana, common in much of central and South America.

The green iguana is very much at home in water.

It has to be, living in riverine forest, often inundated by floodwaters.

It's no rare event for these big lizards to fall into the water accidentally.

They're excellent swimmers and, sometimes, choose this way to get around.

[water gurgling] When you watch the big lizard swimming, the resemblance to the marine iguana is striking.

Hind legs are held close to the side and propulsion comes from sinuous movements of tail and body.

Head and crest are quite similar to the profile of the Galapagos land iguana.

No one seriously suggests that the green iguanas swam a 1,000 ocean miles to make a landfall on the Galapagos, but there was a possible form of transport available to it.

The iguana often climbs on rafts of floating vegetation.

In flood seasons, very large rafts are a common sight on the big rivers of central and South America, and often they make their way out to sea.

So, it's possible that iguanas, lizards and snakes hitched a ride to the Galapagos in this way.

The rafting theory also holds for the probable mainland ancestor of the giant tortoises.

Obviously, this tortoise wouldn't have made it all the way to the islands, but, no doubt, logs carried some smaller reptiles there.

[water gurgling] The ancestral tortoise, Geochelone, is widely distributed on the mainland.

It's a small animal by comparison with the Galapagos giants, but tortoises lacking competition on isolated, oceanic islands are known to evolve into giant forms.

The same thing has happened to the tortoises on the island of the Al Darbara far out in the Indian ocean.

The ancestor of the Galapagos finches probably looked like this little bird, the blue black grassquit.

Ancestral grassquits presumably got blown to the islands in storms.

Cocos Island lying midway between the Galapagos and Central America may have been a wait station for them.

There's a related species of finch found there today.

It's been estimated that no matter how many rafts of vegetation sank, and most probably did, one successful crossing by a pregnant female iguana or tortoise every hundred thousand years would've been sufficient to give the islands their present populations.

But the odds against the immigrants were longer than that.

For many thousands of years, there would've been very little vegetation on the barren islands and, therefore, no food for the new arrivals.

But, eventually, plants colonized the islands.

Many seeds can survive long immersion in salt water and arrived by sea.

A [indistinct] seed is taken root.

Lichens were almost certainly the first plants to establish themselves, but they wouldn't have provided any food nor would a Brachycereus cactus, a fairly recent arrival itself.

Some seeds and spores were wind born.

Grass seeds are often spread by birds.

Gradually, the vegetation built up in this inhospitable landscape.

[wind roaring] This dark-rumped petrel gives a vivid demonstration of how some seeds certainly made the journey to the islands.

At first sight, its plumage appears to be oiled.

In fact, its feathers are weighed down with sticky seeds.

They happen to be the seeds of a tree already present in the islands.

But they could just as easily have been carried from anywhere within such a seabird's wide range.

[bird chirping] The flora of the islands is as peculiar and diversified as its animal life.

Most of the plants possess small and inconspicuous flowers, probably because there are very few insects and, therefore, little need to evolve showy blossoms to attract pollinators.

There is only one species of solitary bee, the Galapagos carpenter bee.

It's thought to be a fairly recent immigrant.

Since carpenters nest in wood, it's likely to have drifted over inside a log.

Nevertheless, it's been in the Galapagos long enough to have evolved into a native or endemic species.

That's the male, he's a bright yellow.

The female is black.

Yellow flowers seem to attract the carpenter bees most.

Among the few other pollinating insects are eight species of butterflies, one endemic, and many species of moss.

[birds chirping] [waves roaring] The difficulties facing those first animal colonists can hardly be exaggerated.

First, a sea crossing of up to a 1,000 miles.

Then a landfall on a coast that is, for the most part, totally hostile to sea-born invasion.

[waves crashing] Third, the likelihood that if you do get ashore, there is no food waiting for you.

And, finally, the distinct possibility that you will never find a mate.

Imagine that you are a mainland tortoise or a green iguana that has survived a month at sea.

You've been washed ashore in the surf and now have to scale an obstacle like this.

Yet against all these odds, enough made it to become the unique Galapagos species we know today.

We'll never know how many rafts of vegetation carrying green iguanas from the mainland sank crossing a thousand miles of sea to the Galapagos.

But the descendants of those first green iguanas which made it followed two divergent paths.

One led to the sea and, eventually, to a new species, the marine iguana.

[waves roaring] It's probable that in their search for food, some of the new arrivals exploited the green iguana's already considerable aquatic talents.

On the rocks and in the tidal pools was a plentiful supply of food in the form of marine algae.

Over many thousands of years, by the process of natural selection, which Darwin described, some of the green iguanas adapted to a watery environment.

[waves roaring] A blunt snout that allowed the iguana to crop seaweed close to the rocks was favored.

Traits that allowed it to stay submerged for longer periods in order to feed also had a natural selection advantage.

One adaptation for this was a slower metabolism which conserves oxygen.

Adult marine iguanas have been known to stay submerged for 30 minutes and can feed at depths of 45 feet.

Exceptionally strong claws and four legs, which helped them cope with surf, were also favored by natural selection.

Marine iguanas seemed to prefer shorelines with powerful wave action.

This is where the seaweeds on which they feed grow best.

Another adaptation to marine life is the flattened tail, which gives propulsion when swimming.

The normally dark skin helps the cold-blooded reptiles absorb heat after feeding in the sea.

[waves lapping] The male iguana with its pronounced crest is quite an intimidating creature.

The bony plates on top of the head play their part in mating fights.

The scientific name for the species is Amblyrhynchus, meaning blunt nose.

The marine iguana allows the finches to clean parasites from its skin.

A lava lizard pulls dead skin from an iguana's tail.

It's another Galapagos species that must have rafted here in the remote past.

In the breeding season, both sexes take on color, though, the degree to which they do so varies between islands.

There are seven subspecies of marine iguanas.

The most highly colored of all come from the island of Espanola.

[birds screeching] Establishment of a breeding territory is very important.

It's won by an eyeball-to-eyeball confrontation between rival males and, sometimes, lasts four or five hours.

These less colorful males come from the island of Fernandina.

Territories can be anything from one to 10 square yards, but they may be just a single block of lava.

The best sites attract the most females.

The less desirable sites are lower down near the water.

In winning and holding his territory, a male may lose a quarter of his body weight over a six week period.

Actual mating with various females takes about three weeks.

[birds squawking] The females have less pronounced crests and are usually smaller.

They excavate the nest and lay from one to three eggs five weeks after mating.

[birds squawking] Then they stay on guard at the nest site for up to 10 days.

This nest hole was probably a trial excavation or one in which she wasn't yet ready to lay her eggs.

That doesn't stop the mockingbird from seeing if there are any eggs to steal.

That failing, they search for insects.

[birds screeching] Young iguanas have several enemies.

One of the most effective is the Galapagos hawk, a powerful raptor well-suited to seizing ground prey.

[birds screeching] The small, non-poisonous Galapagos snake, [indistinct] one more reptile that survived the voyage from the mainland and became a Galapagos species.

It's partial to lava lizards and very small iguanas.

[birds squawking] Today, there are between two and 300,000 marine iguanas in the Galapagos.

Their population is in balance with natural predation.

From time to time, however, a failure of ocean currents affects the growth of the seaweeds on which they feed.

Wide-scale starvation follows.

In 1982, corpses could be seen on every shore after the drastic upset of ocean temperatures caused by the warm-water mass called El Nino.

But such disasters must have happened many times since the first ancestral iguana landed.

No doubt they will happen again.

Only two years after El Nino, the marine iguana population was fast recovering.

[birds squawking] The same green iguana from the mainland is thought to be the ancestor of the Galapagos land iguana.

In evolutionary terms, the land iguana hasn't changed as much from its mainland ancestor as its marine cousin.

But there were a number of adaptations to the Galapagos environment.

There practically no fresh water in the islands, so its jaw had to become powerful enough to break off and crush moisture-containing vegetation like cactus pads and fruit.

It lacks the long claws of the marine iguana, but it doesn't have to cling to rocks in the heavy surf.

Their claws do have to be powerful and blunt for digging their burrows in the soil.

This lava lizard catching flies is in no danger.

Land iguanas are vegetarians and the lizard is doing it a favor.

The iguana's yellow color is in complete contrast to its marine cousin, but then the land iguana's problem is to lose heat, not gain it.

In some ways, the adaptations which the ancestors of the land iguana made, were as foreign to it as those of the marine species.

The green iguana of the mainland had lived largely in lush wet forests.

In the Galapagos, it was faced with an almost completely dry landscape, [insects buzzing] But many lizard species are at home in semi-desert conditions and the land iguana is no exception.

On the six islands where it's still found, it prefers the dry zones with low sparse scrub.

Because of the moisture stored in its fleshy pads, cactus is a favorite food.

The big lizards will even wait under the Opuntia trees for ripe fruits to drop.

[insects buzzing] [birds chirping] Very few animals will eat Opuntia.

It's too well-armed with spines.

The land iguana has developed techniques for dealing with the situation, either by biting between the main groups of spines or by rolling the fallen fruits on the ground to flatten or knock off the spine.

[insects buzzing] [birds chirping] Finches play an important part in the land iguana's life.

The marine iguana is quite happy to let finches clean the parasites off its skin, but it doesn't ask for help.

The land iguana, on the other hand, tells the bird that it needs them by raising itself on all four legs, and that way the finch can do a thorough job.

[insects buzzing] [birds chirping] Though the land iguanas are found mainly in the dry lowlands, there is one notable exception, on the island of Fernandina.

The rising sun unveils the unearthly landscape on the crater's rim of Fernandina's great active volcano.

[bird screeching] The volcanic highlands are the one place where moisture can be found all year round, but it's a difficult and arduous journey to those craters.

At first, over-crumbley lava, then up through arid scrub until the lush green is weak.

Many of the land iguanas of Fernandina make this journey every nesting season.

[bird screeching] It's the soft warm layers of volcanic dust around and inside the crater that attracts them.

The crater rim provides some strange contrasts.

Close to the ash fields grows rich green vegetation watered by condensation from the clouds that often envelop the top of the volcano.

Some of the shrubs bear fruits and flowers, which the iguanas eat during the nesting period.

[birds screeching] The females return to the same breeding areas each year.

They inspect the territories on arrival and it's they, rather than the males, who choose the mate.

[bird screeching] At peak nesting time in July, the volcanic dust is crisscrossed with their trails.

[dust hissing] The female excavates the nest hole and then lays between seven and 23 eggs.

Then she'll mount guard for several days.

[dust hissing] Geochelone, the probable mainland ancestor of the giant Galapagos tortoises could easily have crossed a thousand miles of Pacific Ocean on a raft of vegetation.

It weighs only about 10 pounds.

Even without a raft, it could survive floating in salt water for up to a month.

There are 14 subspecies of Galapagos giant tortoises.

On the largest island, Isabella, the tortoises even differ slightly from region to region.

The tortoises on each of the five volcanoes are separate sub species.

Separated by hostile terrain, they don't interbreed.

These are Santa Cruz tortoises enjoying a mud wallow in the humid uplands at the center of the island.

It was pointed out to Darwin by the governor of the Galapagos that tortoises on different islands had different shaped carapaces or shells.

Those on Santa Cruz are smooth, dome-shaped and low at the front, adaptations that enable them to move more easily through dense vegetation.

The shell of an Espanola tortoise is high in front.

This adaptation allows its owner to reach up for the sparse, scrubby vegetation that Espanola offers.

It's a low, dry island with no volcanic uplands.

The giant tortoises enjoy a regular mud wallow.

You might think that a tortoise wouldn't be worried by mosquitoes, but the soft under parts are vulnerable to their bites.

A good coating of mud offers some protection.

Once there were hundreds of thousands of tortoises in the Galapagos.

Buccaneers, sealers and whalers decimated them for food.

In 1831 alone, 68 ships took 13,000 tortoises aboard.

Sadly, it was often the smaller and easier-to-load females, the sailors caught and ate.

The estimated total population today is between 12 and 15,000 animals, split between six islands.

On Santa Fe and Floreana, they've been extinct for over a century.

As recently as 1980, the remains of 27 tortoises were found on Wolf Volcano on the island of Isabela, slaughtered, its thought, by fishermen.

Their main enemies, however, are pigs, dogs, cats and rats, all animals introduced by man that escaped into the wild.

The story of the tortoises on Pinta Island is an especially sad one.

There's only one survivor, a male called Lonesome George.

He's safe at the Darwin Station on Santa Cruz, but he has no female of his own subspecies to mate with.

[tortoise bellowing] During the breeding season, which varies among the subspecies, the tortoises gather in the moist uplands to breed.

At these times, the highlands resound to the roars of mating males and the clash of giant shells.

Giant tortoises take a long time to mature.

It's believed they're 30 or 40 years old before they reach breeding age.

After mating, most of the females make the long, slow journey down to the arid lowlands to dig their nests and lay an average of 10 eggs in each.

Scientists still argue about the ancestor of the 13 species of Galapagos finches.

But this bird, Volatinia jacarina, the blue black grassquit, is a firm favorite.

This is one of its descendants, the cactus finch.

The Galapagos finches are one of nature's most striking examples of what's called adaptive radiation.

This is when one original species adapts to a variety of local feeding and living conditions in isolated areas.

Over many generations, its physical shape and behavior are altered by natural selection and chance.

With the Galapagos finches, the differences can be seen mainly in the bill shape.

Compare the heavy probing and seed-cracking bill of the medium ground finch with the delicate bill of the tree finch.

In each case, the bill reflects the bird's different style of feeding.

Darwin noted this and it became a key element in his theories on evolution.

The warbler finch, the smallest of all, has the typical bill of a bird that lives by catching insects.

[birds chirping] [insects chirping] The success of the finches is largely because they have exploited a wide variety of food sources.

On Wolf Island, the sharp-billed ground finches have discovered that if they peck at the base of the masked boobies' flight feathers, they draw blood, which provides both food and drink.

So far, this habit has only spread to one nearby island.

Wolf is one of the most isolated of the group.

Perhaps, the habit arose when the finches were cleaning parasites from the booby's wing and drew blood accidentally.

There are no woodpeckers in the Galapagos, but there are a great many rotten trees whose trunks contain insects.

The woodpecker finch and the closely related mangrove finch have found a way of exploiting this rich food supply.

The habit was first observed in the woodpecker finch.

[birds chirping] By no means have all woodpecker finches mastered this trick, so it seems the ability is probably learned rather than inherited.

A woodpecker finch who has mastered the technique starts by breaking off a probe.

Woodpecker finches live in both the arid and moist zones.

In dry areas, the chosen tool is often a cactus spine.

Here, it's a green twig.

The bird usually begins by listening, just as a woodpecker does, to find out if there's an insect at home.

The beak is surprisingly powerful, so the bird has no problem breaking off twigs.

Sometimes, the finch will modify a twig to its liking by snapping off a side shoot.

And they're adept at holding a twig down with one foot while they size up the situation.

Where a real woodpecker would use its sticky tongue to extract the grub from the tree, the finch maneuvers it with a stick until it's within range of its beak.

Incidentally, Darwin never witnessed this most exciting piece of finch behavior.

This time, it drops the stick.

Occasionally, it keeps it for future use.

These two finches have detected a lively grub inside a dead tree.

The dominant bird takes possession and listens at all the available holes.

The grub is quite visible to the finch, but its beak is too short to reach it.

So, the next step is to select a twig.

[birds chirping] Not long enough.

Back to look for a more suitable tool.

[birds chirping] A cutaway section of the tree shows the finch in action with a slightly longer twig.

But this won't do the job either.

The grub is too fat and the entrance to the hole too narrow.

Perhaps, purely by chance or maybe profiting from past experience, the finch selects a third twig that is slightly curved and, therefore, better for getting a grip on the prey.

[birds chirping] Perseverance finally pays off.

[birds chirping] Finches find their food in many ways.

The small ground finch is foraging for ticks on the leathery skin of the marine iguanas.

In this one scene is encapsulated some of the wonders of the islands of the Galapagos.

Here are two creatures, a bird and a reptile that have evolved over hundreds of thousands of years to become new species.

In doing so, they have adapted successfully to one of the harshest environments on the face of the earth.

[birds chirping] [waves roaring] [dramatic music]