The Caledonian pinewoods of the Scottish Highlands.
This patch in the Cairngorms National Park is one of the oldest
remnants of this ancient, wild wood.
It's the stage for an equally ancient drama.
Woodland-dwelling golden eagles.
These birds are clearly at home amongst the open,
old-growth forest.
Golden eagles once flew across much of the uplands of Britain
and Ireland, but are now absent from many areas
due to human persecution.
So, their huge, three-metre nest on the edge of this
wood is now a rare sight.
The nest is home to two fully-grown chicks...
..unusual for golden eagles,
whose stronger chick kills the weaker in 80% of the nests.
Today, the chicks have only been given a tiny weasel.
It could be a way of telling them it's almost time to leave.
Only 1% of these native pine forests are left,
so when the chicks do fledge,
their chances of finding a woodland nest of their own are slim.
Ancient woodlands like these are now rare and precious.
This magnificent oak is a very special tree for me.
I've known it for over 70 years.
That may sound a long time,
but it's only about a tenth of the life of this tree.
It's probably over 700 years old.
In England alone, we have more ancient oaks than the whole
of the rest of Europe put together.
But since I was born, we have lost almost half of our ancient woodland,
and now we are one of the least forested countries in Europe.
Woodland covers only 13% of the British Isles,
and human influence can be seen in every single bit of it.
But despite this, there's a remarkable variety in the woodland
that remains.
Pines in the north...
..broadleaved woodlands in the south...
..and even rainforests temperate ones - along our western shores.
In this episode, we'll take you on a seasonal journey,
to see how animals and plants respond to the challenges of life
in our ever-changing woodlands.
Our journey starts here in the Forest of Dean.
It's winter.
The low, weak sun brings little warmth.
For some, this is a time for slumber.
Hidden away, a tiny dormouse is hibernating.
But not all the woodland residents can sleep throughout the winter.
And one, in particular, has a problem.
The robin.
With snow blanketing the ground,
the robin's favourite food - earthworms - are out of reach.
Luckily, in this forest, help is at hand.
Or rather, at snout!
Wild boar once roamed woodlands right across Britain,
but they were pushed to extinction by the 17th century.
Now they're back,
and although their return hasn't been welcomed by all...
..for this robin, they are invaluable.
The boar use their strong, sensitive snouts to rip up the frozen ground.
This exposes worms - and they are food for the robin.
It's the restoration of an ancient relationship -
and probably the reason why robins follow us around in the garden.
For them, a human with a spade is just a pig on two legs.
As winter loosens its grip - flowers emerge.
Snowdrops are first,
a sure sign that spring is just around the corner.
Soon, more blooms appear, each adding a little colour
to the dark forest floor...
..and inviting insects to spread their pollen.
But while those on the ground take centre stage - the trees above
put on a flower show that is just as dramatic.
Willow catkins attract insects in early spring...
..but small birds also visit,
feasting on the protein-rich pollen.
Yellow smudges of it are carried on their foreheads from tree to tree.
Willow trees are either male or female,
and yews are like this, too.
This group in Sussex are some of the oldest trees in Britain
and they have a different technique to spread their pollen.
On warm days in spring...
..the flowers of the male tree open
and release huge clouds of pollen.
The quantities are so great
that the local fire brigade is sometimes called out by reports
that the forest is burning.
As the pollen drifts away,
some of it may land on a female yew
and, so, fertilise it.
THROAT CLICKS
In the Highlands of Scotland,
something else drifts through the pine forests.
THROAT CLICKS
The voice of a male capercaillie.
THROAT CLICKS
With only around 500 left in these fragmented woodlands,
this is one of the rarest birds in the British Isles.
It's mid-April, breeding season,
and this huge, turkey-sized male is strutting around his arena.
In the trees above, a female, or hen, has arrived.
THROAT CLICKS
The male, or cock, will perform like this
for over six hours, every morning.
THROAT CLICKS
GRUNTS
And it works.
GRUNTS
Several hens have gathered around the prancing,
preening alpha male.
CLICKING AND GRUNTING
But with great success comes great danger.
Until now, the other males have kept well away...
..but powered by a stomach full of pine needles,
a rival enters the arena.
THROAT CLICKING
He's almost a metre tall
and weighs over four kilos.
The two males size each other up,
with a few preliminary pecks.
But with so many hens to fight for - battle commences.
Contests like these can easily end in broken bones - and even death.
The rival is starting to lose face...
..literally. Some feathers have been torn from around his head.
SQUAWKING
He senses defeat and retreats from the alpha's territory.
GROWLS
CLICKS THROAT
Bruised and battered, his time has not yet come...
..but at least he will live to fight another day.
The alpha returns to where the fight started,
tired but triumphant.
His reward is to mate with all the females,
who will then pass on his genes to the next generation.
The species as a whole, however, is losing its battle
to survive in the Scottish Highlands.
Capercaillie became extinct in Britain once before,
back in the 18th century...
..and now a combination of disturbance,
predation and poor-quality habitat
is pushing these birds to the brink once more.
BIRD SOUNDS
Soon these extraordinary sights and sounds may disappear from
our woodlands - for a second time.
In a deciduous woodland just outside London,
the spring sun causes the trees to burst into life.
On the forest floor, a huge mound,
almost two metres high, comes to life as well.
It's a nest of wood ants.
The ants may be tiny, but they are well able to defend their home.
Should any would-be predators approach,
they defend themselves and their castle by squirting formic acid
into the air.
It's a brave bird, indeed,
that would take on this army.
Wood ants are insatiable hunters.
They search the forest floor for food,
swarming over anything that moves
and dragging it back to the nest.
It's thought that a single colony may consume
over six million prey items every year.
And not just on the forest floor.
Up in the trees, caterpillars have emerged
to take advantage of the newly opened leaves of spring...
..so the ants take to the trees
Caterpillars may look defenceless,
but they have several ways of avoiding capture.
The first is to do nothing.
If they stay still, the ants might march on by.
If detected, the second option is to stand and fight.
Some caterpillars have a surprisingly effective bite.
If that also fails, they resort to their third and final option.
They attach a line of silk to a leaf or stalk
and descend into space.
But this lifeline...
..can break.
But these wood ants don't just prey on other species.
They farm them, too.
Aphids drill into the trees
to collect the sap that is their only food...
..and they excrete a liquid waste we call, somewhat flatteringly,
honeydew.
The ants collect it,
just as human farmers collect milk from cows.
The honeydew is shared throughout the colony...
..which may consume a quarter of a tonne in a single year.
From hunting caterpillars to milking aphids,
the ants have a huge impact on the entire woodland.
It's a delicately balanced system,
but the presence of the ants is a sure sign of a healthy forest.
A quiet corner of an ancient cemetery in Surrey.
It's late spring, and a female roe deer is feeding on one of the oaks
that have taken root here.
She is on high alert.
Because with her, amongst the graves,
is new life - her fawn.
Just a few days old
and at his most vulnerable.
Predators have also made a home amongst the old graves.
A fox would make an easy meal of a fawn.
While the youngster suckles, he's safe.
A fox wouldn't dare take on a fully grown deer.
But hiding silently nearby is her second fawn.
Her speckled coat makes her less obvious in the dappled light.
Once her brother has had his fill, he goes off and hides...
..giving her a chance to feed.
Their mother keeps them apart
so that if one is caught, the other might still escape.
Soon, they will both be too big for a fox to be a danger,
but in times gone by,
wolves and lynx would have been a constant threat.
Our woodlands now lack these bigger predators.
Here on the Knepp Estate in Sussex,
grazing animals have been used to recreate a type of woodland
that once covered large parts of the British Isles.
Wood pasture.
In just 20 years, this has produced the conditions needed
by one of our most spectacular insects.
The purple emperor butterfly.
It's midsummer, and from the top of an oak,
the male can watch for females as they emerge from the scrub below.
And he defends his tree-top throne with great vigour.
He's one of our biggest butterflies and will take on any intruder.
He even attacks passing birds.
But only one intruder really matters -
another male purple emperor.
And one has appeared.
The two circle at high speed.
Only by slowing the picture down 30 times can we see what's going on.
They use their 8cm wings as weapons,
attempting to knock each other out of the sky.
The males only live for a few weeks,
so it's all or nothing in this fight.
Soon, a third male appears.
But the resident male sees off his challengers.
His wings may be tattered,
but he's held on to his tiny empire and, with it, his breeding rights.
The Atlantic oakwoods are one of our rarest kind of woodlands.
High rainfall, numerous rivers,
and mild, humid conditions create a lush environment.
These are temperate rainforests.
They have now been reduced to a fraction of their original range
across western Britain and Ireland.
In this patch, in an isolated valley on Dartmoor,
a dream-like scene plays out under the midsummer moon.
An ash-black slug.
Up to 30cm long, these are the largest land slugs in the world.
They are almost exclusively found in ancient, wet woods...
..and on this damp night, this slug is looking for a partner.
It lays down a trail of slime which carries powerful chemical signals.
The scent is an irresistible invitation
to another ash-black slug.
Once the pair reach the tree-tops...
..they become more intimate.
They nuzzle to make sure that they're suitably matched.
Slugs are hermaphrodites,
each equipped with both male and female sexual organs.
Preliminaries complete,
an overhanging branch provides a hold for the consummation.
Twisting together, they hang down as one.
Two penises start to protrude.
Entwining together,
each becomes as long as the rest of its owner's body.
Each slug now passes a packet of sperm to the other.
But the end of the relationship is abrupt.
The left-over slime is the only evidence
that the encounter ever happened.
SQUAWKING
Back in the pinewoods of Scotland, summer is the season of opportunity.
The cones at the top of the trees are now ripe.
A male red squirrel jumps into action.
He starts to feed on the rich, oily seeds the cones contain.
But he is a messy eater...
..and his left-overs alert others to what is now available.
A female.
She is late to the party.
High above, the male sees her coming.
He's in no mood to share.
Driven off, the female considers her options.
If she can sneak around the other side of the tree,
she may be able to arrive unseen.
But in this open woodland, that is easier said than done...
..so she does the one thing a red squirrel usually avoids.
She leaves the trees.
Leaping from tree to tree in old-growth pine woods
is usually impossible, so the deer path is her only option.
That ends where the pine trees give way to birch.
These quick-growing trees stand between the pines
and their slender branches provide alternative access for the female.
One last obstacle remains.
Get this wrong and it's a long way down.
She's made it...
..back to the tree with the ripe pine cones.
And the male hasn't even noticed.
For now.
It's the end of July in the New Forest.
Two honey buzzard chicks are squabbling over their breakfast.
It's late to be nesting, so they need to grow up fast,
and although a frog is not their favourite food...
..beggars can't be choosers.
Frog dispatched, a decent meal finally arrives.
It's the comb from a wasp's nest...
..packed full of protein-rich grubs.
This explains the timing.
Their parents migrated here from Africa to nest
just as the wasps reach their peak numbers in the late summer.
BUZZING
With a ready supply of rich food finally established,
the chicks grow extremely fast.
And they continue to fight.
But, in typical British fashion...
..the weather makes things a bit miserable at times.
It could be why honey buzzards are one of our rarest breeding birds.
You can't always rely on a ready supply of wasps
with summers like ours.
By mid-August, the chicks are growing proper feathers.
The males are mousy-brown
and the female has a handsome white head.
She usually dominates when it comes to squabbles over food.
But there is plenty to go round...
..if you can get your beak on it!
Some of the wasp larvae in the nest are hatching into adults...
..but overlapping feathers provide protection against possible stings.
And a third transparent eyelid,
called a nictitating membrane,
protects their eyes.
It's fast approaching the time when the chicks
will have to leave the nest and fend for themselves.
Flapping the wings builds their strength.
And every day the chicks gain confidence.
If not elegance.
By late August, their time has come to leave.
The female chick takes her first ever flight.
Followed a few flaps later by her brother.
They will soon set off on a 3,000-mile journey to Africa...
..escaping the approaching chill of our autumn days.
With the arrival of the new season,
our woodlands begin to shut down.
The leaves change colour...
..and a hush descends on many of our forests.
But not all of them.
ROARING
Fallow deer bucks have gathered to fight for the right to mate...
..advertising their presence by roaring.
They were introduced in the 11th century by the Normans
and initially kept in private parks.
But they soon escaped and spread across much of the British Isles.
The does watch on.
They're likely to mate with the biggest
and most persistent roarer here...
ROARING
..but the choice is theirs.
Some males thrash the undergrowth.
ROARING
And antlers become adorned with foliage.
This young buck...
..has yet to impress.
But he hangs around the edges, just in case.
The frequency and quality of a buck's roar
is an indication that he's in good condition.
BUCK ROARS
But, if a challenger approaches,
the next step is the parallel walk.
If it's an obvious mismatch,
they might still save their energy.
But this looks as if it could be a fair fight.
ANTLERS CLASH
The bucks can weigh up to 100 kilos.
A wrong move now could be fatal.
In the pandemonium, other males join the battle.
BUCK ROARS
As they fight, the does sidle away.
They join the small male on the edge of the wood.
Although his technique still needs a little improvement...
..this could be the young buck's lucky day.
SOFT ROARS
As the sounds of the rut fade,
hitherto hidden players in the woodland drama appear.
Fungi.
The cool, wet days trigger an eruption of mushrooms
and toadstools across the forest floor.
These are the fungi's fruiting bodies
and they have just one function -
to spread their spores.
Some simply allow their spores to slip out of the gills
beneath their caps.
Others wait for a gust of wind to carry theirs into the air.
Puffballs rely on the rain.
One droplet is enough to trigger the projection of a puffball's
spores far and wide.
Mushrooms and toadstools can be highly visible,
but they are only a tiny part of each fungus.
And it's only recently that we have started to understand what
some of these organisms are doing when they're out of our sight.
Underground,
mycorrhizal fungi send out a web of tiny filaments
called hyphae.
These soon encounter tree roots.
The two organisms then connect.
And now they can share resources.
The fungus gets sugars from the trees,
and the tree gets water and minerals from the fungus.
And the sharing doesn't stop there.
The fungi link trees and plants together
in a mutually beneficial network called, by some,
The Wood Wide Web.
We can see how this web works
by speeding through the year in this Suffolk woodland.
After a winter of dormancy,
the woodland in spring bursts to life.
Excess resources stored by the mature trees
move through the fungal web
and give sprouting saplings a good start.
But new growth attracts leaf eaters.
Plants under attack emit distress signals.
By using specialised equipment,
we can listen to these signals as they travel through the web.
WHISTLES AND BEEPS
This is the sound of plant communications,
and those that detect it can activate chemical defences
so that if they are attacked,
their leaves are already distasteful.
Summer brings its own danger - drought.
Young trees may struggle
as their limited liquid reserves are depleted.
But the network can come to their rescue once again.
Water moves from deep-rooted trees to others in greater need.
These complex relationships exist in every woodland,
and 90% of all our plants depend on them.
But such networks take time to develop.
Ancient, diverse woodlands
have more fungal connections
and support more life than young plantations
that contain just a single species.
Such monocultures usually consist of fast-growing, non-native trees,
that today account for almost half of all our tree cover.
This plantation,
hemmed in by farmland on one side and Bodmin Moor on the other,
is cold, dark, and inhospitable.
But birds are using this wood as a temporary home,
and its branches are caked with the evidence.
As the late winter sun begins to sink,
the tenants return.
RUSHING SOUNDS
Starlings.
They've been out feeding all day,
but, as the cold night draws in, their numbers start to increase.
Up to a million birds will use this small plantation
as their overnight roost.
But others know this.
Buzzards hope to snatch a weak bird from amongst the flock.
TWITTERING AND RUSHING
And, up above, a peregrine.
The starling flocks swirl and coalesce
as they react to the predator's presence.
There's safety in numbers.
By gathering in huge flocks,
the chances of getting caught are reduced enormously for any one bird.
The light starts to fade,
and the starlings come down to roost.
As their numbers increase, so does the noise.
INTENSE TWITTERING
In this chatter is information.
Birds continue to join the roost long after the sun has set...
..revealed by thermal cameras.
They pack ever more tightly into the plantation.
Until, to our camera,
the trees are illuminated like skyscrapers at night.
In close-up, it becomes clear
that there are vigorous arguments over the best perches.
Because, even now, the starlings are not safe.
A barn owl.
Wraith-like, it hovers above the roost,
causing panic among the birds perched beneath.
The owl takes its time.
It is a remarkable hunting technique,
revealed for the first time
by using these specialist cameras.
As soon as dawn arrives,
the birds leave to resume their feeding.
The size of these winter flocks may give the impression
that starlings are doing well,
but in fact, their numbers in recent years
have diminished by 80%.
Our woodlands are now expanding,
but the new plantations are mostly of low diversity.
We need to give better protection to the native woodlands that remain...
..restore those that we have lost...
..and allow our trees the time and space to spread, naturally.
It will take many years to recreate anything as rich as the woodlands
that we once had...
..but surely it should be our target to do so.
To reveal the intimate lives of two very different bird species,
two teams filmed in two distinct types of woodland
at opposite ends of our isles.
In Scotland, a family of eagles
take advantage of the open and spacious old growth forest.
While in Cornwall, this dense strip of plantation
is a winter roost for nearly a million starlings.
They're well known for their astonishing murmurations,
but the team want to get a more intimate look,
and reveal what goes on in the roost after dark.
To do that, they need to get amongst the closely planted trees,
where it's dark, lifeless and rather smelly!
Urgh, that's gross.
This all looks pretty fresh.
You can see, like, a good couple of centimetres
of bird poo on the branches.
As well as the visuals of all the birds coming in,
we're trying to get... I'm really keen to try and get
a real multi-sensory experience as much as possible.
Sadly, we can't share the smell,
and it's coating the ground as well, so there's probably,
yeah, a good...
..four or five centimetres of bird poo there as well.
So this definitely feels like
it probably is the centre of the roost.
Having sniffed out the roost,
the team build a platform
so that they can rig remotely operated cameras
up in the canopy.
We've got the full tower up now, so we're pretty much
at the top of the trees,
which really feels like you're in the middle of the roost.
Hopefully the birds will surround us
and we'll be able to get some nice, intimate close-up shots of them.
The remote cameras allow cameraman Jo Charlesworth
to hide out of sight below.
So, everything's working.
As long as the birds don't fly into the other end of the woods,
it's just a case of waiting for them to arrive.
450 miles to the north,
cameraman Hamza Yassin is searching the Scottish Highlands
for golden eagles, and their nest.
I'm hiking through this amazing, amazing ancient woodland.
There's still snow on the ground as you can see,
and it's Baltic!
With only 20 pairs of tree-nesting golden eagles
in the whole of the British Isles,
finding a nest that the team can film is no easy task.
Hamza climbs to a good vantage point,
where he can scan as much of the forest as possible.
It's a waiting game.
So, I'm scanning the high ridge line there,
waiting for the golden eagles to pop up,
and then figure out where they're coming
down to their nest.
Yes, we have contact!
The first golden eagle has been spotted,
and it's only...6:30 in the morning.
Come on!
Their nest is likely to be nearby.
They're bringing in nesting material,
which is the best thing ever,
but still doesn't show me where the nest is exactly.
Halfway there, halfway there.
The next day, Hamza drives closer to pinpoint where they are.
Ooh, here we go, here we go. Come on...
Ah, finally!
An adult leaving the nest
reveals its exact location.
Three days' work has paid off.
That's incredible.
The team can now return later in the year
to film the chicks when they hatch.
In Cornwall, the starlings are arriving back at their roost.
Jo's hard work pays off,
and he captures the starlings
as they crowd into the canopy around his cameras.
It gives a unique insight into what it's like to be amongst
a million roosting birds.
TWITTERING
And the team also record the sound of the flock
as they settle down for the night.
INTENSE BIRD CHATTER
This is actually insane now.
We're literally in the middle of a starling roost.
But the following day, the roost is silent,
the birds have disappeared.
You would have thought a million birds, or thereabouts,
might be quite easy to spot.
Apparently not.
We're pretty sure they must be in the area, but...
it's a big old area.
While Chris has lost a million birds in Cornwall,
in Scotland, the eagles are right where the team want them to be.
In a hide installed by the estate,
cameraman John Aitchison is able to film right into the nest.
So, at the moment, I can see in the tree...
which, I have to say,
is probably the most beautiful eagle's nest I've ever seen,
in the top of a big Caledonian pine - a Scots pine tree.
They're just carrying on with their lives.
Especially if I'm quiet,
I shouldn't make any difference to them at all.
Director Lily watches from the other side of the valley.
They're exceptional parents.
They're bringing in food constantly.
That nest is so well-stocked.
The hard-won view of the rare nest gives the crew
a special insight into the lives of these tree-nesting eagles.
There's so many things that I've learned
over just these ten days being here,
and it's been a real privilege getting to know these birds.
Capturing these intimate moments
took a huge effort from the crew,
working alongside the local team
who protect this ancient forest and its inhabitants.
Back in Cornwall, the team have found the starlings,
and it's time to take things a step further.
A thermal imaging camera allows them to film the starlings
in a new way, revealing their behaviour in the roost after dark.
There's something very Christmassy about it.
All these trees festooned with light.
And they capture the exact moment that a night-time predator arrives.
Yes! Yes! Good spot.
A barn owl, only visible with the help of the thermal camera.
The intimate moments captured in these very different forests
are proof that many spectacular animals
still call our woodlands home.
These are important habitats.
From the gorgeous, gorgeous golden eagle
up in that nest in the Cairngorms,
down to the starlings using this apparently pretty low-grade
woodland on the edge of Bodmin Moor,
every little bit is really important
and we've got to look after it - it's precious and it's special.
Next time...
..grasslands...
..where hidden stories...
..meet epic dramas.
The Open University has produced a free poster
exploring our Wild Isles
and their diverse habitats and species.
Order your copy by calling...
..or go to the website and follow the links to the Open University.
If you'd like to play your part in the story of our Wild Isles
and learn more about what you can do to help,
just search "Wild Isles" on the BBC website.