Spring - Season of Extremes Highlands - Scotland's Wild Heart

Scoured by ice and weathered by storms...

..20,000 square miles of rugged coastline, lochs and mountains.

On the face of it, it looks bleak and lifeless...

but wildlife is thriving in this unforgiving place...

..if you know where to look.

The seasons may be harsh...

..and the opportunities fleeting.

But animals and people have found ways to succeed here,

turning adversity into advantage.

This is Scotland's wild heart

- the Highlands.

It's late March in the Cairngorm mountains and the hills are on fire.

The old heather is being put to the torch

to stimulate new growth for the grouse season.

Traditionally, this inferno marks the end of winter

and the start of spring in this wilderness.

But spring is the most unpredictable of all the seasons in the Highlands.

Temperatures regularly range from -10 to 20 degrees.

So, to achieve success here, animals have to battle with the extremes.

It's all about timing.

Mate, nest, or give birth at the wrong time and lives can be lost.

But get it right and these mountains, forests

and rivers provide the perfect place to raise the next generation.

BIRD CHIRPS

It can be so good that some travel thousands of miles to reap

the bounty the Highlands has to offer.

It's an osprey.

Newly arrived from his wintering grounds in West Africa

and heading back into the heart of the Highlands.

200 pairs of ospreys make the Highlands vast network of river,

loch and mountain their home.

The hills start to rise just 20 miles north of the country's

Central Belt and cover two thirds of the entire nation.

To most of the world, the Highlands define what Scotland is all about.

BIRD CAWS

One mile south of iconic Loch Ness,

this valley has been home to breeding ospreys for a decade.

OSPREY CALLS

The female is already on the nest, waiting for her mate.

They've spent the winter in different parts of Africa

but osprey's mate for life

and now they're reunited on the same nest they used last year.

But, after the gales of winter, it needs some urgent home improvements.

Already more than five feet wide, this platform will need to

withstand strong winds, heavy rain and maybe even sleet or snow.

They need to complete the makeover as quickly as possible

because, once the eggs are laid, the female won't leave the nest

until she's raised her family.

For the next 13 weeks, she'll be completely dependent on the male.

Spring's the busiest time for the animals in the valley.

Brown hares, curlews,

and stoats are all getting ready for the breeding season.

This male roe deer is keeping close watch on a female,

but she won't let him near.

She's already heavily pregnant

and searching for a quiet spot to give birth.

The next few days will be critical for all the wild animals here.

A new generation is about to arrive.

But the conditions are still far from settled.

Although it's now April, the temperatures still haven't

climbed above 10 degrees and clouds hang heavy

from Loch Awe in the west to the Cairngorms in the east.

But, in the great Caledonian pine forest of Abernethy,

there's change in the air.

It's a red squirrel.

Although they've been displaced by grey squirrels in most

of Britain, they're thriving here in the Caledonian Forest.

There are 120,000 of them in Scotland -

75% of the British population - and they're increasing.

The habitat here is ideal for them, with abundant food

and plenty of potential nest sites.

With double jointed ankles and small, sharp claws,

they can get up and down trees fast.

Early spring is a busy time for red squirrels.

Already pregnant with kittens, this female is

looking for a comfortable nest site, away from predators.

She'll either build a drey from twigs and leaves

or use an uninhabited tree hole.

She'll need to keep searching.

But this female's territory is large,

she's got 17 acres of pine forest and river to search yet.

50 miles beyond the forest, on the River Braan,

a pair of special Highland birds have already built their nest.

They're dippers, birds that are marvellously

adapted for life in this fast-changing environment.

Britain's only aquatic songbird, dippers have waterproof plumage

to keep them dry, and long, flexible feet for gripping slippery rocks.

Their white bibs and dark bodies keep them well camouflaged as

they dive for insect larvae amongst the boulders and rapids.

In spring, these are in plentiful supply.

DIPPER CHIRPS

The dippers are working nonstop as they've already got

hungry mouths to feed.

Carefully covered by a neat moss dome,

the nest's position may look dangerous...

..but it offers total protection from predators

like stoats and weasels.

Food goes in and waste comes out.

Even a large fish is delivered,

an indication that the chicks are well-grown.

For now, the river's level is just right for the chicks to make

an easy exit.

But if heavy rain arrives, the waterfall will become a torrent,

which could sweep the nest away.

At last, the weather is warming.

For the first time this year, temperatures climb to 15 degrees.

It's now a priority for the Highland animals to feed themselves up,

ready for the next phase of spring.

Over the next couple of months, the male osprey will need to

catch more than 400 fish to keep his family going.

He makes hunting look easy but it's a game of stealth and patience.

Only one in four strikes are successful.

He needs to find a fish in the right position and get the speed,

angle and point of entry exactly right.

After hitting the water and grabbing the fish,

the game still isn't over for the osprey in its quarry.

He needs to get airborne again.

His talons are equipped with adhesive scales

and long, curved claws for an unbreakable hold.

But a big trout can match him weight-for-weight

and the instinct of the fish is to swim down.

There are tales of weak and hungry ospreys being dragged to the bottom,

unable to release the fish or lift off from the water successfully.

But osprey wings are adapted to give maximum lift from the water.

And this male is young and strong.

This is a struggle he's destined to win.

He carries the fish headfirst,

making it easier to fly the 20 mile journey home.

Back in the valley, the female waits in the nest.

Their need to feed is even more urgent now.

She's no longer alone in the nest.

There are definitely chicks in there!

They're not the valley's only new arrivals.

Deep in the long grass, at the edge of the field, lies another new baby.

With immaculate camouflage, it instinctively lies motionless.

The roe deer has given birth.

Leaving her offspring alone like this

seems like a high-risk strategy.

But the mother needs to feed

and the youngster is too young to run away from danger,

so hiding is the only option.

The mother approaches warily.

She mustn't reveal the location to any watching predators,

like eagles or foxes.

But it's not predators that are the greatest threat to young roe deer.

A sudden drop in spring temperatures could be fatal.

The male osprey is back with the fish.

He's now got a lot more mouths to feed.

There are three hungry chicks in the nest.

Fuelled by their high protein fish diet, osprey chicks become

full size in just five weeks.

And once they're 12 weeks old, they face an even bigger test.

A flight to distant Africa.

Just one mile north of the ospreys' valley lies the Great Glen.

Once a mighty glacier, it divides the Highlands in two.

At its heart is the most famous body of water in Scotland...

..Loch Ness.

It deserves its legendary reputation.

23 miles long, it contains more fresh water

than all the lakes in England and Wales combined.

As for the monster...it still hasn't been found.

But the Highlands are full of mysterious creatures.

POPPING NOISE

It's 4am in Abernethy Forest, and something is stirring.

Capercaillie - the world's biggest grouse.

There are just over 1,000 left in Scotland...

..and their stronghold is here in the pine forest.

Their bizarre popping call penetrates deep into the forest.

It attracts the females to a ritualistic display

called a lek.

Here, in a forest clearing,

the males will compete for the right to mate exclusively

with all the females.

Weighing in at more than 4kg,

this young male is in superb condition.

But an older male is up for the fight, too.

This veteran, with a bald patch on his neck, has been

king of the lek for many years.

The females look on from the treetops desperate to see

which suitor will be victorious.

It's time to raise the stakes.

Game on!

They're evenly matched - it's simply a question of who gives way first.

The younger male is on the run...

handing victory to the dominant, older bird.

Like an Emperor of the forest, he's retained mastery of the lek.

All the females are his.

Nearby, the female squirrel is feeding on pine cones.

The small seeds between the scales are a protein-rich food source

and she needs extra nourishment now.

She's just given birth.

There are two new kittens,

hidden deep in her drey high up in a Scots pine.

Soft moss is ideal for lining the nest.

Squirrels are fastidiously clean animals.

But the tiny and blind babies can't leave the nest for a toilet break.

So, regularly changing the bedding is an important part

of the female squirrel's routine.

Although the drey is only ten inches across,

it takes at least six mouthfuls of moss to fill it up and make it snug.

Once the youngsters are able to grip and climb,

they'll start leaving the drey to explore.

But that's still many weeks away.

So, for now...she's stuck with this time-consuming chore.

High above Abernethy Forest, snow is still lying thick

and deep on Cairngorm, Cairn Toul and Ben Macdui.

But it's 1st May, and spring is picking up pace.

Further down on the moorland edge, wild flowers are coming into bloom.

Bumblebees are buzzing... and newborn lambs are playing.

There we go, shall we empty your bucket, Ernestine?

But despite the sunshine, the hill farmers know that it's still

too early to risk taking the sheep on to the mountains.

Even in May, heavy snow can fall in the Highlands,

so, for now, they'll feed them here in the valley, close to the farm.

SHEEP BAA

But for the wild creatures of the Highlands,

there's no chance of holding back and waiting for better conditions.

They just have to make the best of it, whatever the weather.

Tawny owl and wagtail chicks

are already on the verge of independence.

And the osprey chicks are growing fast, too,

demanding more and more fish from the male.

The roe deer can sense change is coming.

Her youngster is now more mobile

and she's instinctively moving it towards higher ground.

It could be a wise move.

This valley has flooded many times in the past.

She can't help it across the fence.

Now it's a week old, it has to work the problem out for itself.

FAWN CRIES OUT

THUNDER RUMBLES

The weather has taken a turn for the worst.

It's deteriorating fast.

Temperatures are sliding into single figures

and a cold front is now sweeping in from the Atlantic.

Heavy rain is on its way.

THUNDER RUMBLES

The three osprey chicks huddle beneath their mother's wings.

The nest is vulnerable now.

Spring downpours like this have been known to destroy osprey nests.

But for the dipper family, the situation is far more serious.

Practically a month's rain has fallen in 24 hours

and the river is still rising.

The torrent has completely obscured the little nest and the adults

can only get in and out by flying behind the wall of water.

It's the worst possible time for the chicks to fledge.

But the adults are calling them out.

There's no option now.

If they stay inside any longer, they'll be drowned.

They're in mortal danger.

Young dippers are weak flyers. One mistake and it's all over.

One across.

The other four seem reluctant to go.

The female has stopped feeding the chicks to encourage them out.

If they're to eat, they must leave.

They're using the same route as the first chick.

But the surface is wet and slippery.

There's just one left in the nest.

It's made it across. They're all out on their own.

The chicks are desperate for food.

But rather than help her young, the females goes straight back to

repair the nest for a second brood.

The desire to reproduce is more powerful than feeding

the newly-fledged young.

Without guidance from the adults,

the chicks could still be washed away.

This one's far too close to the edge.

But the male is calling him upriver, away from danger.

Little...by little.

And, at last, he gets his feed.

Now for the first dip.

Dipper chicks need to swim well from soon after they emerge.

In a week, their father's attention will end

and they'll have to catch their own food.

Despite the perilous location, dippers have nested here

on this Highland river for many years.

And, hopefully, will be here for generations yet.

At last, after two days of constant rain, the weather has cleared.

The osprey nest is intact...

..the young roe deer is thriving...

..and the squirrel kittens make their first forays from the drey.

Now temperatures are rising.

And the Caledonian pine forest is awakening.

Warmed by the rays of the sun,

the understory now seethes with life.

They're Scottish wood ants.

Over six feet wide and teeming with a colony 100,000 strong,

this nest has stood in the heart of the forest for decades.

With the sun now high overhead, the ants will do everything

they can to get the benefits of the warmth it brings.

Teams of female worker ants sunbathe on the surface in shifts.

Once they've heated up, they travel deep into the nest,

to transfer their warmth to the eggs and larvae in the brood chambers.

On the forest floor, ants swarm along regular trails

capturing insects to bring back to the nest for food.

Because these insects eat plants, this, in turn, protects trees

and saplings from destruction.

So, remarkably, these tiny ants safeguard the future of the forest.

Rare timberman beetles also emerge in spring.

With antennae four times the length of his body, this is

the longest insect in Britain and another real pine forest speciality.

He's just emerged as an adult,

after spending two years as a bark-eating grub.

And he's on a mission to mate.

Quite why the antennae are so long is something of a mystery

but it's certain that picking up the smell, sound and taste

of a female beetle is a major reason for their incredible length.

He's got a female in his sights.

A successful meeting.

The female will now lay her eggs in a suitable cleft in the bark,

but it will be the last act of her life.

The adult beetles live for just a couple of months.

Back in the valley, the osprey chicks are exercising

their young wings in the sun.

They're almost ready to fly.

And they're not the only ones enjoying the warmth.

Common lizards live in the dry-stone wall beneath the nest.

The Highlands are on the very northerly edge of their range

as they can't live without sunshine.

So now is the time they're most active.

They're safe from the fish-eating ospreys but they do have enemies.

Adders - Scotland's only poisonous snakes.

The lizards need to constantly watch for danger.

But, today, the snakes are unlikely to strike.

They're about to shed their skins.

Yawning wide may help stretch the skin to help it split.

But the moult will take many days..

..and the lizards are safe...

..for now.

OSPREY CALLS

The female osprey's calling in alarm...

..and down go the chicks into the bowl of the nest.

There's an intruder in the valley.

It's another osprey, a male who's failed to find his own

territory this year and he wants to move in.

He wouldn't try to kill the chicks but if they were

knocked from the nest they'd be unable to fly back to safety.

That's far too close.

Time for direct action from the male.

And up flies the female.

Female ospreys are much bigger than males

and quite capable of seeing off an unwanted intruder.

Especially when there are chicks in the nest.

The family is safe.

It's now only a matter of days before the youngsters

make their first flight.

The wheel of the seasons is turning...

..and spring is rapidly becoming summer.

The mountains and glens are at their greenest as the natural world

enters its busiest time in the Highlands.

And nowhere is this more evident than in the sea.

Here in the Moray Firth, a pod of dolphins are heading to a feast.

They're bottlenose dolphins, one of 23 different species

of cetacean that have been seen off Scottish coasts.

Nearly 200 individuals have been recorded here socialising,

breeding and hunting together.

They usually seek out mackerel, squid and herring

but there is one species of fish that the bottlenose dolphins

prize above all others...

..Atlantic salmon.

With Highland rivers now swollen to the brink, due to heavy rain,

the fish are heading towards the interior to start their journeys

to the spawning grounds.

And the dolphins will be waiting for them.

The best place to ambush the fish is Chanonry Point near Inverness.

The tidal run here means the fish are directed

into a deep and narrow channel

where the dolphins wait

to ambush them in the murky, fast-moving water.

Very big fish are running today. Some are 20lbs or more.

But swallowing such a huge fish isn't easy.

They need to slip down in exactly the right way and that means

regurgitating and reswallowing until the position is exactly right.

Sometimes twisting your body actually seems to help.

And down it goes.

Over the next few weeks, the dolphins will be catching more

and more salmon as the fish start their migratory

journey into the heart of the Highlands.

But other migrants will be leaving the Highlands behind.

In the valley, there are big changes.

All three chicks have learned to fly and are spending longer

and longer out of the nest.

Now the chicks can fly independently,

their parents are preparing to switch roles.

For nine weeks, the male has caught every single fish

while mum has delivered all the care in the nest.

Now the entire burden of childcare will shift to him.

For the next fortnight, it'll be his job to teach them

all he knows about how to soar,

dive and catch fish before they head off on their epic migration.

As for the female, relieved of her parental duties, she's already on

her way south, starting out on the 3,000 mile journey to West Africa.

The extreme spring weather of the Scottish Highlands provides

endless challenges for all its residents.

But animals here are resilient, adaptable and strong.

For them, these mountains,

forests and rivers offer unmatched opportunity.

That's why the ospreys will return here year after year.

Back to their home, in Scotland's living wild heart.

Next time...

Highland animals race towards independence before summer's end.

Young otters need to stop playing and learn to catch fish.

Golden eagles ceaselessly hunt for mountain hares.

And tiny guillemot chicks face a desperate leap for life

as they fall to the sea from 400-foot cliffs.