The male alone is responsible for building these showcases.
Females regularly tour the bowers, assessing their riches.
The arrival of one stimulates the male to posture and strut.
But she's not yet decided.
There may be a more impressive bower elsewhere.
A rival and more dominant male appears.
He steals the treasures while the proprietor is away.
He does more. He's not only a thief but a vandal.
He uses the remains of the demolished bower to reinforce his own.
He now has the most spectacular collection of decorations
in the whole neighbourhood.
This individual embellishes his treasury in another way.
He paints its walls with blue paste made from mashed berries.
It's all done to impress the female.
If she is going to mate, it is between the walls of the bower
that she will receive him.
These little black and white birds are mannequins.
Each male has industriously cleared for himself a little dancing court.
They're all so obsessed with dancing
that they don't just do so for a few weeks but for nine whole months!
And what is more, for 90% of daylight hours within those months.
The males keep their courts meticulously clean and tidy.
They perch together amiably enough above their courts,
but when a female appears, their mood changes.
Now each does his best to impress her with his dancing skill.
The strange noises are produced by the males
snapping their wings behind their backs
and clicking special flight feathers.
It seems as if they are flying backwards,
as they manage to make a mid-air turn just before they land.
Mannequin dances vary greatly from species to species.
The club-winged snaps as he jumps,
and adopts a posture that draws attention to his scarlet cap.
Blue-crowned mannequins fly in circles around their perches.
The golden-headed favours a backward shuffle.
That movement is elaborated further by the wire-tailed,
who flicks the female across her chin with long filaments from his tail.
But these long-tailed mannequins are even more extraordinary,
for both are males.
The female has just landed on the right.
This is a double act. She will only respond if two males perform.
But why should apparent rivals help each other?
One is senior, and he owns the dancing perch.
Only he will mate with the female.
The other is his apprentice who is learning the form.
And indeed this dance takes some learning.
Young males start practising in their second or third year.
They get their adult plumage at four,
but continue to dance with younger birds like this one.
Only when he's eight will he become an apprentice
to a male who owns a court.
If his senior partner dies,
he may inherit the court and take on his own apprentice.
But he'll only succeed in mating
if the females are impressed by the virtuosity of his team performance.
This male antelope, a topi, is also defending a court.
It wasn't until just recently that we realised
any mammals displayed like this.
And that's just what's going on here in the plains of Kenya.
I'm sitting on the edge of just such a display ground.
Immediately behind me are the two best courts.
Each is held by a male who's trotting around,
inspecting the half-dozen or so females, who also have horns,
who've come to visit him today.
He sniffs one to discover whether she's ready to mate.
Within yards of these central courts stands a less successful male.
He has a court, but not the best, and no females have joined him.
The courts are so close
that rivals often come face to face on the frontier between them.
As long as they don't cross the line, their disputes are only symbolic.
As the day warms up, more females thread their way through the courts
to the central ones held by the most successful males.
This young calf is accompanied by its mother.
She's ready to breed again, but not with this low-ranking male.
He nonetheless tries his luck.
He crosses the frontier of his court,
and immediately his neighbour gallops across to repel the invasion.
The successful males in the centre courts
have acquired more females than they can manage.
The least successful bulls hold courts around the edges.
It's hot, and they're very tired, but they won't leave.
Only by competing can they graduate eventually to a premier position.
These marginal courts, being close to tall grass, are dangerous places.
A hyena.
For a topi, the cost of courtship can indeed be high.
The rewards for all these displays, persuasions and entreaties, however,
can certainly be great.
Yet even coupling may not be the ultimate achievement it seems.
An animal may have to do more than this
if it's to ensure its genes will pass on to the next generation
and so transcend its mortality.
That will be the final trial.
(PEOPLE SINGING IN SAMOAN)
This is Samoa, in the middle of the Pacific.
It's October, the moon has just entered its third quarter,
and the villagers have come out onto the reef,
because this is an extraordinary moment.
On this one day of the year, around dawn for about an hour,
the sea produces the most delicious food that people ever get from it.
The water becomes alive with millions upon millions of worms -
palolo.
To be accurate, each wriggling thread is only the back half of the worm.
The head ends are still safe within burrows in the coral reef.
But these tail ends contain the all-important sex cells.
The yellow threads are male, the green ones female.
The segments disintegrate as they reach the light,
releasing their contents.
Milky sperm oozes out
and meets the green eggs spilling through the ruptured body walls.
Fertilisation is achieved, and on an astronomic scale.
So this simple animal, by a feat of timing we still don't understand,
solves the problem facing all animals striving for biological success:
how to pass on their genes to the next generation.
But though the problem is always the same,
the solutions are amazingly varied.
Barnacles, stuck to the rocks groping for food,
face a particular difficulty when it comes to mating: they can't move.
Their solution is a male organ
that proportionately is the longest possessed by any animal.
And they have another aid to mating.
Each barnacle possesses both male and female organs,
so every neighbour is a potential mate.
Eggs are only produced once a year, and as soon as they're ready,
it advertises the fact by releasing a chemical,
and all its neighbours reach across to try and fertilise it.
Unlike eggs, which require a lot of energy to make,
sperm can be produced quickly and in quantity,
so, as a male, a barnacle can fertilise many others.
They all compete to do so,
and the egg bearer is given far more sperm than necessary
and ejects most of it as a white blob.
So the barnacle gets the best of both the male and the female world.
Most animals must settle for one or the other, which complicates things.
The female Madagascan tortoise has to summon her male.
She does it with her perfume, but when one turns up, she plays hard to get.
He, however, is armed.
He has a spike on his shell so big that it gives the species its name:
the ploughshare tortoise.
He's unable to force her to mate,
but he can use his spike to demonstrate his strength in a very convincing way.
Her perfume has attracted another male.
The rivals must fight it out.
With his opponent overturned, the victor can claim his prize.
The female, having righted herself, seems sufficiently impressed by his strength
to accept him as the most powerful male around.
And the vanquished can only lie by helplessly.
Female elephants have a similar way of sorting out the men from the boys.
Producing a calf takes a long time -
22 months of pregnancy, then four years of feeding it on milk.
So she wants to make sure her calf has the best father around.
She becomes sexually receptive for just a few days every four years.
Mature bulls spend most of their time away from the herd,
wandering in special bull areas.
So it's usually a teenage hanger-on who first notices her availability.
But he's not yet very good at mating,
and he's not the strong partner she wants, so she leaves him.
The male she seeks is a mature bull like this 50-year-old.
Males are only in full sexual condition for three months of the year.
This one is. A gland behind his eye is discharging.
His genitals are dripping. He's in musth.
During this time, he devotes his energy to seeking out females.
He assesses their condition by smell.
If a female's smell is promising, he tastes her urine to test it.
It's as important for her as for him to make clear her reproductive state.
(RUMBLING)
The deep rumble is being made by a female.
Her partner has deferred to the big male,
but her call proclaims she's still receptive.
The big male begins to follow her.
She encourages him with a special swinging walk.
Each time she's mated, she calls again,
in case there's a bigger musth male around.
By the end of her receptive period when the egg enters her womb,
she will be partnered and guarded by the biggest male in the neighbourhood,
and he will be the father of her calf.
Crabs wear suits of armour which makes mating impossible,
but this male has detected a taste in the water
that tells him the little female is about to shed hers.
As soon as she slips out of her shell, while her new one is still pliable,
they can become intimate.
He's going to hold onto her so no other male can claim her
at that crucial moment.
Her moult has begun, her shell has split underneath,
and he is helping her to disrobe.
The empty suit of armour in front
makes it seem as if he has two females in his embrace.
The fact it's merely the ghost of her former self
is revealed by its vacant eye sockets
and the way the current blows it about.
The female, her new shell still soft and leathery, crawls beneath him.
He fertilises her swiftly before her shell hardens.
She won't be able to mate again until her next moult.
Soon he will abandon her, but, like the bull elephant,
he has ensured that the egg she'll nurture will carry his genes.
A male blue gill sunfish swimming in a lake in North America
seems big, strong and confident enough to take on any rivals.
He's eight years old, and he, too, is ready to breed.
He hollows out a shallow nest by fanning his tail.
Then he sets about persuading one of the females nearby
to come down and join him.
He's offering both a nest and his parental services.
One arrives.
Although she's considerably smaller, she is full-grown,
and he chivvies her into his nest to lay.
She catches his mood from his distended fins and circling dance.
Things are going well.
But lurking in the weeds is a tiny two-year-old male.
He will never build a nest or woo a female,
but he's a serious rival nonetheless.
As the female lays, he darts in and delivers a jet of sperm.
Back he comes to add another squirt before he's finally chased off.
The owner of the nest continues his dance.
The more eggs that are laid in it, the better.
The little sneak retires to the weeds.
The big male seems to have been joined by a second female.
Not so. The new one in the middle is an older sneaking male.
He dances so like a female the big male doesn't notice the difference.
The nest owner chases away other males,
leaving the female impersonator with the real female,
unhurriedly fertilising her eggs.
Eventually, the big male is left in sole charge of the nursery.
He labours away, fanning the eggs
to keep oxygen-rich water flowing over them.
He's a devoted father, steadfastly guarding the fry when they hatch.
Two thirds of them are probably not his.
Baby lily trotters, jacanas,
are also left in their father's charge.
Unusually for a bird,
the female defends the territory and mates with three or four males,
who build the nests and look after the broods.
A strange female is trespassing on this breeding territory.
There are eggs here, so the male should be nearby.
He returns to protect them, but he seems to be alone.
The intruder lurks in the weeds, watching him with interest.
Finding a male alone probably means his mate's been killed,
and her territory and all her males could be up for grabs.
He displays aggressively towards her, trying to drive her away,
but females are bigger than the males and she is not to be deterred.
He is of no use to her while he broods another female's eggs.
She starts to smash them, and he is unable to prevent her.
They were on the verge of hatching.
Having destroyed his brood, she now offers herself to him.
And the bereaved male mates with the murderer of his chicks.
She succeeds in getting rid of all the chicks not carrying her genes
and replaces them with those that do.
One female with many mates is unusual.
In most polygamous relationships
it's the male with the harem of several females.
And that is the arrangement here.
A full-grown male sea lion comes ashore in Patagonia
early in the season to claim a patch of beach
and start assembling his harem.
The females all arrive within days of one another.
They're only a third his size, and he tries to keep many close to him.
Young males come, too.
They're not big enough yet to win battles for females.
Within a day or so of arriving,
the females give birth to the pups conceived a year ago,
almost certainly on this very beach.
Six days after the birth of her pup, a female becomes sexually receptive,
and the beachmaster, who has taken her into his harem, mates with her.
The best sites for a harem are above highwater mark,
but now the beach is very crowded,
and even the less good positions are occupied.
At the edge of the central breeding area,
males without a harem prowl around looking for a chance to mate.
There's an atmosphere of suppressed violence in the colony.
A young male rushes into the breeding area.
As the harem-holders are forced to fight,
others see a chance of winning something from the confusion.
An intruding male tries to abduct a female.
He will rape her if he can.
The violence spreads.
A young male who has still not mated works off his frustration on a pup.
So the ways in which males and females can come together
and raise their young are huge.
I, because of my particular species
and the society in which I happen to have been reared,
tend to think that the monogamous pair, husband and wife,
staying together long enough to share in raising the young, is the norm.
But actually, in the animal kingdom, it's very, very rare.
One of the few creatures that also does that is this beautiful bird...
...the royal albatross.
These two birds first mated over 20 years ago,
and they have been together ever since.
They met as five-year-olds, on these cliffs where they'd hatched.
While their elders nested,
they joined with others of their own age to dance.
(CONSTANT CALLING)
As the dance parties proceeded,
the male and the female began to dance together habitually.
After a few weeks of these courtship games,
the young birds flew back to sea.
During the year that followed, they cruised the oceans separately,
looking for fish,
but the following year they were both back.
By now they were regular companions during their time ashore.
Then the male claimed a nest site.
At last, after four years of courtship, their alliance was consolidated.
The permanence of the partnership was essential,
for a chick takes nearly a year to be big enough to fend for itself at sea.
During that time,
each parent must make voyages of several weeks to collect food,
and be so faithful that it flies back hundreds of miles to feed its chick
and relieve its near starving partner who has been its lonely guard.
If you watch animals objectively for any length of time,
you're driven to the conclusion that their main aim in life
is to pass on their genes to the next generation.
Most do so directly by breeding.
And the few examples that don't do so by design,
they do it indirectly by helping a relative
with whom they share a great number of genes.
Inasmuch as the legacy that humans pass on to the next generation
is not only genetic but to a unique degree cultural,
we do the same.
So animals and ourselves, to continue the line,
will endure all kinds of hardship, overcome all kinds of difficulties,
and eventually the next generation appears.
This albatross is over 30 years old.
She's already a grandmother, and this year, once again,
she's produced a chick.
She'll devote the next 10 months of her life looking after it.
She has faced the trials of life and triumphed.
For her little two-day-old chick, the trials are just beginning.