The Blue Planet

The coast - the frontier between land and sea.

This is the most dynamic of all the ocean habitats.

The challenge here is to survive change,

extreme change.

Cape Douglas, on the most westerly Galapagos island,

totally unprotected from the massive rollers of the Pacific,

and one of the roughest coastlines in the world.

The marine iguanas of the Galapagos

are the world's only sea-going lizards.

Seaweed is all they eat, but doing so is a dangerous business.

The local crabs have become specially flattened,

minimising the effect of the pounding waves.

And the iguanas have huge claws to grip the rocks.

This seaweed really is fast food.

There are only a few seconds in which to grab a few mouthfuls

before the next breaker comes pounding in.

Females feed only on the exposed rocks,

but the larger males dive beneath the surface to reach the weed.

They go as deep as ten metres,

for there, below the destructive waves,

they find the best fronds.

Cold-blooded, they have to return to land after about ten minutes

to warm up again in the sun.

Finding food is not the only challenge for coastal residents.

These rocky shores are hardly a safe place to lay their eggs.

Each year, the marine iguanas

have to journey inland to find a more suitable one.

The females lay their eggs in burrows

and leave them there to hatch.

To do that, they need nice soft sand.

Down at the water's edge, it was easy to escape danger

in rocky crevices.

Up here, the females are dangerously exposed.

A Galapagos hawk.

The lizards don't give up without a struggle.

These hawks stay on the coast all year, but they are exceptional.

Most of the birds that frequent this frontier

spend most of their time in or above the open ocean.

However, all seabirds have to come to land in order to lay their eggs.

And, after many lonely months spent searching the ocean for food,

they have to re-establish social relationships.

Frigate birds display

and exchange nest material.

Waved albatross dance.

The need to lay eggs on firm ground ties the albatross to the coast,

but parental responsibilities are shared.

While one looks after the egg, the other can go off to feed.

The need to breed brings many different animals

to the coast each year for a few weeks.

Male sea turtles spend all their lives at sea,

but the females, like birds, must come to land to lay their eggs.

To do that, green turtles that live and feed off the coast of Brazil

swim 1,500 miles to the tiny island of Ascension,

that lies bang in the middle of the Atlantic 0cean.

How they manage to navigate with such accuracy

and find this tiny lump of rock just seven miles wide is a mystery.

But, each year, up to 5,000 turtles manage to do so,

and then, close to the coast of Ascension, they mate.

Travelling to and from Ascension and nesting can take six months.

Throughout the entire time, none of them feed at all.

After mating,

a female has to leave her natural element and haul herself onto land.

She does so at night, laying three or four times at 15-day intervals.

After that, she swims back to the seas off Brazil.

She returns to this very same island throughout her life.

Remarkably, all the world's sea turtles return, year after year,

to a few traditional breeding sites.

Crab island in Australia is one of them.

This tiny two-mile long crescent of sand,

lying a few miles off Queensland's northerly tip,

provides nesting sites

for half the population of one of the rarest sea turtles.

Flat-backed turtles are over a metre long,

but they have to be careful -

there are other giant reptiles here, too.

Salt-water crocodiles.

Every night throughout the year, there are flat-backs

burying their eggs all along this stretch of sand.

Nine weeks later,

and things are about to happen.

These eyes shining in the darkness belong to night herons.

As if from nowhere, hundreds of birds appear on the sand dunes.

Pelicans wait patiently.

jabiru storks pace up and down.

Before long, they see what they've been waiting for.

Because these turtles lay their eggs throughout the year,

the hatchlings emerge nightly in a steady trickle of beak-sized meals.

The pelicans' broad beaks allow them to dig out the hatchlings

before the herons can spear them on the surface.

The surf may be hundreds of metres away

and at least a third do not survive the journey.

it's not just the birds that take them.

Crocodiles, sharks and hungry fish are all waiting in the shallows.

in fact, only one in 100 hatchlings will survive to adulthood.

Another beach, another continent and a very special night.

in Costa Rica, a turtle has found a way of reducing these dangers.

When Ridley's turtles arrive to lay their eggs,

they don't come in tens or hundreds, but in thousands.

in the next six days, around 400,000 females will visit this beach.

At the peak time, 5,000 are coming and going each hour.

The beach gets so crowded, they have to clamber over one another

to find bare sand where they can dig a nest hole.

40 million eggs are laid in these few days.

These turtles ensure that six weeks later,

when their hatchlings emerge, it's not just a trickle.

it's a flood!

0n some nights, over two million hatchlings

race down to the sea together.

With so many appearing simultaneously,

the predators are overwhelmed.

Most of the turtles reach the sea safely.

Leaving the sea and emerging onto land is hard enough for turtles.

it's even harder for fish.

Each year, for hundreds of miles along the Newfoundland coast,

capelin throw themselves onto the beaches.

At least a million tonnes of fish floundering out of the water -

a real gift for scavenging eagles and gulls.

0dd though it may seem for the fish,

the capelin, like the turtles, have also come out of the sea to breed.

The males are trying to fertilise the eggs

that the females deposit in the sand.

Like the Ridley's turtles, they've synchronised their mass laying with the tide.

in a few days, it will be over.

Most of the capelin die,

but only after they've left their eggs in the sand.

0ther capelin populations lay their eggs in the ocean,

so why do the Newfoundland fish spawn on land?

it seems that eggs deposited on the beach are safer from predators

and develop faster than in colder waters out to sea.

But, wherever they do so, the huge spawning shoals

provide the concentration of food that seabirds need

when THEY assemble to breed.

95% of the world's seabirds nest together,

mostly in large spectacular colonies.

This is Funk island, 40 miles off the coast of Newfoundland -

an isolated rock crammed with breeding seabirds.

This was the last breeding ground for the flightless great auk,

sadly now extinct.

Today, it's still the world's largest guillemot colony.

0ver a million of them share this island with 250,000 gannets.

it's not the lack of suitable sites

that causes seabirds to breed in such densities.

Here, in the North Atlantic,

there's a wide choice of empty coastline the birds could use.

The key factor limiting seabird colonies

seems to be availability of food in the surrounding ocean.

There are lots of hungry mouths to feed

and a constant demand for fish.

Throughout the long summer days, at colonies like Funk,

there's a continual stream of birds heading out to find food

and returning with full crops to feed their young.

Gannets will travel up to 200 miles from the colony

on a single foraging trip.

They are not fussy eaters

and will take everything from tiny sand eels to herring.

Puffins, on the other hand, are particular about what they eat.

Because they can only fly short distances,

they only nest where there is a good supply of food close by.

0ne such place is the Sea of 0khotsk in far eastern Russia.

This is the island of Talan.

Throughout the long Arctic winter it is encircled by ice.

But as spring approaches, that begins to break up,

and seabirds that have wintered far to the south

begin to return.

its isolated position and steep cliffs

make Talan a perfect nesting site.

The tufted puffins arrive first.

These are the Pacific cousins

of our less spectacular Atlantic species.

Horned puffins soon follow.

in all, 14 different species return to Talan each spring.

in a few weeks, the silent cliffs

come alive to the calls of four million breeding seabirds.

This is a multi-storey avian city.

Assembling in these colonies,

after having spent a largely solitary life at sea,

provides the birds with the social stimulation

that is the key to co-ordinating their breeding.

By nesting and laying together,

they ensure that most chicks will leave the nest at the same time.

Like the turtles, this is the way they spread the impact of predators.

The world's largest eagle - Steller sea eagle -

a third as big again as a golden eagle.

Throughout the summer, the eagles hunt in Talan's crowded colonies.

Riding on the updrafts, they patrol the cliff tops,

looking out for any kittiwake

that ventures too far from the rock face.

The huge eagle swoops with the aerial agility of a falcon.

Co-ordinated panic among the kittiwakes confuses their attacker.

But the eagle doesn't give up.

And it has got one.

Another kind of seabird on Talan

has a particularly effective way of defending itself against predators,

but it doesn't appear until an hour before sunset.

As if from nowhere, dense swarms of seabirds suddenly arrive offshore.

They've spent the day feeding far away

where the sea ice has already broken up.