Few birds have caught the human imagination as powerfully as the eagle.
Throughout the centuries, this majestic bird of prey
has been the symbol of strength and courage,
such is the perfection of its design.
There are 60 different kinds of eagles throughout the world
and all have this basic body plan.
But eagles hunt many different kinds of prey,
and to succeed they've had to adapt the classic eagle blueprint,
and these modifications have been spectacular.
This is the signature of the world's most successful eagle.
In terms of design, the golden eagle is a classic model.
With just a few modifications, it has colonised much of the world.
The trademark of all eagles is a hooked, rapier-like bill,
but they use other tools for killing.
The back talon pierces like a bayonet.
The rest act like grappling irons, crushing prey with an incredible force.
Its surveillance gear is equally powerful, magnifying two and a half times
and resolving eight times more detail than the human eye.
It can see prey a mile and a half away.
Flight reveals another defining feature - broad wings that float on air.
In the slightest updraft, five kilos of bird becomes as light as a feather.
Through evolution, prey has become the natural designer,
refining each eagle's body plan and behaviour.
In Alaska, a cauldron of early morning mist shrouds another classic model,
one specifically for fishing.
(HIGH-PITCHED SQUAWKING)
The icy advance of the Arctic winter has driven golden eagles further south.
But for the bald eagle, the Chilkat River
provides a welcome staging post on their migration.
(SQUAWKING)
The black and white livery is the trademark of many fish eagles.
The steamy backdrop has formed,
as thermal springs percolate the river like a natural jacuzzi.
Up to 3,000 bald eagles gather here,
enticed by the fishy banquet hidden beneath the icy surface.
Volcanic heat acts as an ice-breaker,
allowing salmon to spawn during the cold heart of winter.
These are chum salmon.
Having spawned their next generation, they're waiting to die.
Like vultures, the bald eagles simply have to bide their time.
The pickings are easy, but the competition is fierce.
(SQUAWKS)
He proclaims possession, but still needs to feed quickly.
(SQUAWKS)
Fights are highly ritualised.
(SQUAWKS)
Pride, the only injury.
A high concentration of food allows many eagles to co-exist.
A fine balance between tolerance and aggression results in ritualised combat.
(SQUAWKING)
They might slip and slide, but grip pads on their talons will clamp the slipperiest fish.
Their two-toned uniform means birds with food become flying advertisements,
easily seen by other birds.
(SQUAWKS)
But bald-eagle etiquette allows the bird in possession a moment to feed
before the raider attacks.
It might look like a bun fight, but among the scrum the birds are taking turns.
Ultimately, they all have a seat at the table.
All fish eagles share similar characteristics and most are gregarious.
In contrast, other eagles tend to be solitary.
Among them are the powerful forest eagles of the tropics.
A long tail and short wings is their unique brand mark.
The crowned is Africa's most ferocious eagle.
(BIRDSONG)
Its crested headgear only adds to its imposing appearance.
It hardly needs such embellishment.
The nature of its prey says everything about its power.
In response, the eagle has developed awesome weapons.
The crowned is marvellously adapted for forest hunting.
The long tail gives manoeuvrability,
while short wings squeeze it through the smallest gap.
Forest eagles have a body plan shaped for hunting in woodland.
Golden eagles could not survive here, although, by changing their behaviour,
they have invaded some surprisingly wooded places.
In the Dadia mountains in Greece, golden eagles hunt over open forest,
but their long wings create problems when chasing their prey among the trees.
They have found an unlikely alternative prey.
Soaring as a search technique is equally effective
for finding tortoises.
But stooping seems like overkill
and to avoid crashing into trees, it applies the brakes as it nears the ground.
The armoured shell presents an intriguing challenge.
It simply doesn't have the right tools for the job.
Its solution is ingenious.
It flies to a favoured site, where a rocky outcrop acts like a natural anvil.
It then gains height.
It then safely parachutes into the clearing.
The impact separates the tortoise shell into two halves - like loosening a lid.
Eagles here feed almost exclusively on tortoises.
They've all learned the same trick.
(SQUEAKS)
In forests, tree nests are common, but too many trees and the eagles can't hunt,
even for tortoises.
Dense forest has acted as a barrier,
preventing the golden eagle reaching South American and South-East Asia.
But it nests throughout Europe, North America and Asia,
making it the most widespread and successful of eagles.
Strangely, the golden doesn't nest in Africa. The reason why involves other eagles.
These are steppe and lesser-spotted eagles riding a thermal on their way to Africa.
Using broad wings for lift, they glide from this invisible elevator in search of another.
They're now over Israel.
By gliding from thermal to thermal, they will save energy on the long journey ahead.
Using this energy-saving flight,
they may travel as much as 4,000 miles without stopping for refuelling.
They undertake this marathon flight because in their home on the steppes of Asia
their mammal prey hibernates over winter.
Steppe eagles are smaller relatives of the golden eagle, but only they migrate.
By the time one reaches Africa, it's lost a third of its body weight.
In their northern homes, they feed on small mammals, but here their tastes change.
There are 16 other eagle species in Africa,
so to avoid competition, the steppe needs to find a gap in the food market.
Besides scavenging, it eats mainly termites.
Its African cousin, the tawny, prefers small mammals,
so the two avoid conflict by pursuing different prey.
Another way of winning the endless competition for food is to be the biggest.
The martial weighs in at six kilos, with a wingspan of over two metres.
This huge and ferocious bird can show surprising tenderness.
Just a single chick is reared every two years -
family planning that matches the number of birds to the available space.
Amazingly, each pair of martials needs 100 square miles to itself.
Big birds not only need a lot of space, they also hunt big prey.
Even small antelope like this duiker are tackled.
The hunter exploits cover as far as possible. Surprise is everything.
Even an eagle as powerful as a martial only succeeds one time in five.
The bateleur has a bizarre and unique shape that helps it find a meal.
It intersperses its ungainly flaps with short glides, trying to gain height.
Its tail is too short to serve as an effective stabiliser.
But soaring reveals the effectiveness of its body plan.
Its comparative instability responds instantly to the tiniest updrafts.
The short tail makes tiny, quick adjustments, allowing it to soar at low altitude
as it looks for carrion.
With scarcely a wingbeat, it can search 200 miles in a day.
As it lands, its aerial grace vanishes again.
Its flight technique allows it to survey huge areas
and spot carcasses that other eagles miss.
With such a diversity of eagles in Africa,
it seems surprising that the golden isn't among them,
but perhaps it is.
Soaring above the rock kopjes of the Matopos in Zimbabwe
is the answer to the mystery of the missing eagle.
These are black eagles.
Except for the colour of their plumage, they're almost identical in form to the golden.
To survive here, the archetypal generalist - the golden eagle -
has had to become a specialist.
(SQUEAKS)
Remarkably, it now hunts just a single prey - a distant relative of the elephant.
Rock hyrax may look like rodents,
but their hooves hint at this closer and more surprising relationship.
The landscape of broken rocks offers their prey a maze of escape routes.
To increase the element of surprise, eagles often collaborate in pairs.
They add to their prey's confusion by hunting with the sun behind them.
But the hyrax has evolved a countermeasure - an iris in its eye that cuts down the glare.
Being detected might seem to be the ruin of a hunt,
but this eagle is a decoy, attracting attention away from its teammate.
For black eagles, competition starts with hatching.
This chick is unlucky.
It's three days younger, and here sibling rivalry can lead to murder.
The parents are attentive, bringing back garlands of aromatic leaves
to use as fly repellents.
The black eagle uses this natural insecticide to fumigate the nest, as many eagles do.
But her devotion will not help the new hatchling.
The older chick has summarily dealt with the competition.
This may seem harsh, but it has good reason.
In the tropics, there are few vacant territories.
Even one extra eagle may have trouble finding a space.
In temperate zones, populations turn over quickly.
So there eagles spread the risk by rearing more.
But here, one offspring is the more prudent investment.
Laying two eggs is an insurance policy
just in case one, for some reason, is lost.
With so much competition in Africa, any new environment is soon fully colonised.
These are the skeletons of trees
drowned when Zimbabwe's Kariba Dam was created in the 1950s.
They now provide perches and nest sites for the African fish eagle.
This species shares many characteristics with the American bald eagle.
They both have a bill perfect for filleting and talons that act as fish spears.
They also have grip pads on their talons
and long, slender legs that snatch their prey from the water.
Because of internal reflections,
the fish can only see out of the water through a narrow window directly above.
The fish eagle exploits the fish's blind spot when hunting.
It swoops in low and takes the fish by surprise.
(SQUAWKS)
Despite the occasional slip-up,
they're so efficient that they can sometimes spend as little as eight minutes a day hunting.
There is only one type of fish eagle in Africa, so it has no direct rivals.
It's found wherever there is water.
But not all water contains fish.
This is Bogoria, a soda lake in Kenya.
No fish live in this caustic waterˇ­ˇ­ but eagles still hunt here.
Their prey are flamingos.
The fish eagle is spoilt for choice.
Up to two million flamingos may congregate here.
(CACOPHONY OF FLAMINGOS SQUAWKING)
Several pairs of eagles live on the lake, but they never seem to breed here.
Perhaps the flamingos are too heavy to carry to the nest.
As the flamingos filter algae from the caustic water,
they always keep a watchful eye on the sky.
The eagle seeks out weak or isolated birds.
Its technique is to prevent the prey getting fully airborne.
Dive-bombing weakens the bird.
The fish eagle may have adapted to new food, but so have other eagles.
The scavenging steppe eagles that first took us to Africa
have here become pirates.
For the fish eagle, it's easier to hunt again.
It leaves the fighting to others.
(SQUAWKS)
It's not only eagles that are its competitors.
Black kites mob fish eagles relentlessly.
Talons can be formidable defensive weapons, but contact is rare.
Such aerial manoeuvring has developed into highly ritualised displaysˇ­ˇ­
ˇ­ˇ­ among some fish eagles.
The white-bellied fish eagle lives along the coasts of South-East Asia.
But here, near Penang, competition comes from a surprising and dramatic source.
This aerial battle is for territory.
An eagle may rest from the fray, but by simply watching the dog fight,
it risks losing airspace.
These fights demand precision-flying and often climax with the presenting of talons.
As the eagles push their stunt-flying to the limit, they make contact.
Talons lockˇ­ˇ­ and the eagles spiral.
These spectacular contests are highly ritualised.
And Talon-grappling is one of the most astonishing displays of aerobatics in the natural world.
Cartwheeling is a game of dare that can end in death.
The ultimate test of nerve.
Other eagles cartwheel, but fish eagles are the stars.
Forced to fight over the same food, they have become skilled in the art.
This is not an eel. It's one of the most venomous snakes on earth.
It needs to be handled with care.
Sea snakes congregate here to breed.
The eagle has refined its hunting skills to such a degree
that it can grapple with this potentially lethal prey.
The eagle has no immunity to the venom, so it's forced into a deadly juggling act.
Power-diving ensures that the snakes are taken by surprise.
Fishing over the open sea has led to its wings becoming long and narrow,
a shape more common among sea birds.
This fish eagle has been able to adapt its fishing technique to a different prey,
but the forest contains eagles that make hunting snakes a speciality.
The crested serpent eagle belongs to a group known as the snake eagles.
Such a specialist prey needs a radical re-shape of the eagle.
It's adapted for walking and climbing, allowing it to search in dense woodland.
To tackle potentially venomous prey, it pays to take it by surprise.
Its small size and relatively short wings allow it to fly amongst dense foliage.
This serpent eagle has adapted to forest life.
It's a home that it shares with another group of eagles.
Short wings for saving space and a long tail for manoeuvrability
is the recurrent solution for a life in the forest.
It's a blueprint that has been perfected by the hawk eagles.
This is Blyth's hawk eagle.
Its conspicuous crest is found in most forest birds and is probably a signalling device.
Long claws on the talons are for plucking birds from the air,
for this eagle is a fast and dynamic hunter.
It's also tiny.
It's among the smallest eagles, being no bigger than a pigeon.
Being small has advantages in the forest.
In other environments, eagles have found advantages at the opposite end of the scale.
Japanese fishing boats off Hokkaido are a magnet to the world's biggest fish eagle.
With a two-and-a-half-metre wingspan and weighing in at an incredible nine kilos,
these Stellers are the sumo wrestlers of the eagle world.
Closely related to the bald eagle but twice the size,
they have a bill larger than any other bird of prey.
The fishing fleet provides easy pickings - the fish that fall from the nets.
Even large fish are just a sushi snack for these huge eagles.
Stellers are among our rarest eagles,
but as much as a third of the world's population may gather here, drawn by free seafood.
Remarkably, in strong winds,
even the heavyweights sometimes have problems losing height.
They may have to spill the air from their wings by whiffling.
As they squabble over these free handouts,
the heaviest and largest of the fish eagles profits from human activity.
In the Philippines, the greatest of the forest eagles is not faring so well.
This is the mighty Philippine eagle, surely the most impressive of all the family.
Its headdress is a flamboyant crown that outclasses any other eagle.
At over a metre in height, this is the world's tallest eagle.
Its splendid crown only enhances its record-breaking size.
Like the crowned eagle of Africa, its talons are for monkey-sized prey.
In the air, it is no less impressive.
Its wings are very broad and have a surface area larger than any other eagle.
This shape is suited to slow flight and manoeuvrability in the forest.
But this eagle holds a less enviable record,
that of rarity.
This is the first film taken at the nest in the last 20 years.
Philippine eagles rear just one chick.
This one is three months old.
It will be another six months before it's fledged. The parents will not breed for another two years.
Such a low turnover suited a world before human intervention.
The eagle is now unable to reproduce quickly enough.
This remarkable view of the world's most endangered eagle removing a monkey's tail
is now, sadly, a rare sight.
The Philippine eagle's forest home is rapidly disappearing.
(THUNDER)
As the rainforest vanishes,
so, too, do the eagles.
Fewer than 200 may now remain in the wild.
The fate of this magnificent forest eagle now rests in human hands.
Among the world's largest eagles, the golden eagle group has its own star.
The distinctive tail of this huge eagle has given the species its name.
The wedgetail is derived from the golden eagle.
When it arrived in Australia, it found a continent empty of other eagles.
Without competition, it evolved unchecked.
Even young kangaroos aren't safe from this fearsome hunter.
It's found throughout the outback and is Australia's only large bird of prey.
Its population exploded when forests were cleared for grazing
and it thrived on the introduced rabbits.
Now an introduced virus is wiping out its new rabbit prey,
so it's turning back to the old.
Such young kangaroos present a challenge,
but its lance-like talons have been known to pierce a lung and even kill adults.
In the hunt, the fan-like tail gives quick manoeuvring.
But even the fast turns that such a shape allows can be outmanoeuvred.
Hunting traditional prey is difficult,
but today there are more modern ways of getting meals.
Roadside eating is the labour-saving alternative.
There are no vultures in Australia, and the wedgetail has taken on their role, too.
The wedgetail is a golden eagle whose habits have diversified in the absence of competition.
But even the archetypal golden eagle can show similar versatility.
This is Kamchatka, a remote wasteland in Eastern Siberia.
Golden eagles are only able to survive here because of the presence of Steller's eagles.
Here the Stellers fish for spawning salmon as the bald eagles did in Alaska.
Only Stellers have bills strong enough to break through the sockeye's armoured skin.
But the golden eagle shows the adaptability of its superb body plan
by becoming a scavenger.
It needs to feed quickly, but by taking its chances,
it can survive in one of the most inhospitable places on earth.
No other eagle is so successful.
It's a living testimony to the perfection of a classic design.
More than any other, this flying masterpiece lays claim to a simple accolade - the word "eagle".