The Life of Birds (1998) s01e07 Episode Script

Finding Partners

(vARIETY 0F BIRDCALLS) This lava gull in the Galapagos, like all the rest of those birds, is sending a very clear message with its call.
It is saying, ''I'm ready to mate and I have got a great place for a nest''.
Some birds send the same message but use an additional medium: not just sound but vision, as these frigate birds are doing.
Their visual signal is normally an inconspicuous patch of shrivelled skin on the throat.
It takes about twenty minutes to blow one up.
The females, who don't have a throat pouch, cruise by assessing what is on offer.
The size of the balloon gives them a good indication of a male's vigour, and therefore his desirability as father of their chicks.
A female takes a closer look.
Males who haven't yet got a nest keep a close eye on developments.
The female leaves, and one of the homeless males decides to make a challenge.
The throat pouch is an obvious target.
Tear that and its owner won't be able to attract anyone.
A new proprietor takes over the nest site and pumps up his balloon.
Success is swift.
She's found what she was looking for.
A male hornbill's brilliantly-coloured beak and wattle is also an indication of his fitness.
Having attracted a female's attention, he accompanies her on flights through the forest, and, at appropriate moments, he cements their relationship with a few judicious gifts.
A little fruit.
Males world-wide ingratiate themselves with females in this way.
Wattled guans do in the tropical forests of Amazonia, and so do great tits in the suburban gardens of Europe.
Seabirds, of course, like fish, though it is still the prerogative of the female to decline a gift the first time it is offered.
Grebes like fish, too.
These are on a lake in North America.
But for grebes in particular, exchanging presents is only the beginning of courtship.
There's a lot of dancing to be done before the partners are sure they are meant for one another.
Their first routines involve repeating one another's movements.
0nce they have got to know each other really well, however, they perform their pas-de-deux together with immaculate timing.
Their wings don't contribute much to their costumes.
Like those of all diving birds, they are short and stubby.
But the dancers make up for that with impressive footwork.
After the dancing, more gift-giving.
weed from the bottom of the lake, a sample of what the couple intend to contribute when they make their nest together.
A male swallow-tailed gull also declares his intentions with a down-payment on the nest.
As a pair get to know one another better, they become sufficiently trustful to indulge in a little mutual preening.
Albatross behave in the same way.
These powerful bills are quite strong enough to injure anything or anyone that dares to interfere with the birds.
But now, as the pair sit together on their nest site, they are used to deliver the most tender of caresses.
What follows may seem like duelling .
.
but actually it is, once again, a kind of dancing.
The sequence of movements is long and complicated.
If both partners perform without mistakes and in harmony, then, at last, there comes the most intimate act of all.
Mating in birds can be a very quick business, no more than a brief meeting of genital openings.
In albatross, it is unusually leisurely.
So pairs are formed and the union is consummated.
For most birds, the pair will now stay together for several weeks, if not for several years.
In the case of these waved albatross in Galapagos, they will stay together for the rest of their lives.
And that, when you come to think of it, is very unusual Insects don't stay together, frogs and toads don't, lizards and snakes don't.
Why should birds? Well, the answer isthere.
No female bird can manage to fly around with an egg inside her - let alone several - for the days or weeks it needs to develop.
As soon as she can, she lays it.
But then caring for it is a major job.
And for these albatross, as for most birds, it's a job for two.
It would be nice to think that such a devoted pair were held together by mutual affection.
The evidence, I'm afraid, doesn't support that.
It's not so much the affection that one bird has for the other, as the concern it has for its own genes, which are in the egg the two produced together.
If, without jeopardising those, either bird could find a way of spreading its genes more widely, the evidence suggests they would take it.
Here in Jamaica, some male birds are far from faithful Flame trees, when in flower, produce great quantities of delicious sweet nectar.
It is the staple diet for hummingbirds, and Jamaica has many different species of them.
The male streamer-tailed hummer is a vigorous and aggressive creature, and a particularly strong individual will take control of an entire tree.
0ther males, of course, have their eyes on it.
But the resident male won't allow others near his flowers, even though you might think there is more than enough for everyone.
But he is not fighting just because he wants to drink all the tree's nectar himself.
He is more devious than that.
The tree is the most prolific source of nectar around.
There are several female streamer-tails in the neighbourhood, and they are busy building nests, which they do entirely by themselves.
They are relatively plain creatures, lacking the long streamer-like tails of the male.
There is so much nectar around that when the time comes they will be able to feed their chicks single-handed.
But the main supply comes from the flame tree, and, sooner or later, they all visit it.
The male streamer-tail waits for them to call.
As soon as one appears, he shows off in front of her with a special courtship flight.
He erects little tufts like ears on either side of his head.
She accepts him.
He goes back to wait for the next diner, while she pulls herself together and prepares for life as a single parent.
A good secure home can also be a very effective lure with which to attract a female.
Red-headed weavers in Africa often nest in colonies and when they do, the females, who have yellow heads, keep an eye on which male is building what before committing themselves.
This one is only just starting.
It's too early to judge his skill as a builder.
This looks promising, but perhaps it's still too early to tell.
A lot of work goes into each nest.
It's very important that the weave should be tight.
If it's too loose, the eggs might drop through.
When one is finished and ready for judging, the male perches hopefully beside it.
She clearly doesn't think much of this one.
This, however, is good enough to warrant an internal inspection.
If she accepts, she will add the lining herself.
But there are lots of females around, and as soon as she's settled in, he starts building another nest.
In fact, this particularly skilled and industrious male has already built three earlier nests, each of which now holds chicks that he has fathered.
Each female, by choosing him as a mate, has provided her young with the best genetic inheritance available.
And he, by keeping on building, has quadrupled the number of his offspring.
But some birds construct even bigger buildings to impress females, and to see the most spectacular of all, you have to come to the dense forests of the islands north of Australia.
Some females can be persuaded to mate for rewards that are more abstract than mere food and lodging.
There's a kind of bird here in New Guinea whose females select a male, not because he is a better meal-ticket, but because he is a better artist.
How else would you describe this wonderful construction except as a work of art? This is its creator, the Vogelcop bowerbird.
He has a passion for interior decoration.
His hut, almost big enough for me to crawl into, is neither a home nor a nursery.
It is a gallery in which he can display his artistic creations to visiting females.
These flowers come from a creeper that has only just started to bloom, great new material for anyone who likes colour.
And he loves it.
The iridescent wing cases of beetles also appeal to him, and he has amassed an impressive collection.
But they are always in need of a little rearrangement to show them off to their very best advantage.
He calls to invite female visitors.
There are several such bowers in this part of the forest.
A hundred yards away, there is another one built by another male of the same species, who has a slightly different artistic sense.
If a female decides this is the best selection of jewels, then she will mate with the owner.
So here, where living is easy, a female is not bowled over by practical things such as food or accommodation.
It's beauty that wins her heart, and beauty can be found not only in jewels but in costumes.
This is Bulwer's pheasant, and he's got spectacular wattles.
He's impressive enough when he is going about his normal business, but when she is around, he gets very excited indeed.
Impressive though he is, she is very critical He's not good enough, it seems.
Another pheasant, Temminck's tragopan.
His costume jewellery is even more elaborate.
And if you've got it, why not flaunt it? The male monal pheasant impresses his female with a greater expanse of unbroken iridescence than is possessed by any other species.
The argus pheasant has the largest of all tail feathers, and wing feathers that are certainly as spectacular.
And what can rival the train of a peacock? The costume put on specially for courtship dances by the African widow-bird may not be quite as extravagant and unwieldy as those of the pheasants.
But the widow-bird displays by flying with his.
It's a hazardous business exposing yourself like this, even if you can fly.
You are making yourself an easy target for a hawk, and there are many around on these grasslands in Kenya.
Evidently the additional matings a male gets from displaying in this dangerous fashion make the risk worthwhile.
Up in the frozen north, on the Arctic tundra, life is altogether too rigorous to allow such extravagance.
Here males display in a more modest way.
The buff-breasted sand-piper.
No spectacular plumes for him.
But, nonetheless, he has quite an attractive armpit.
Flashes like these can be seen a good two hundred yards away.
A female has got the message.
She's definitely interested.
Now there are three females.
It's time to reveal all.
He reinforces his appeal with quiet clicking calls.
More and more females arrive.
Nearby, another male is having no success whatsoever.
Now there are four females with male Number 0ne.
This hardly seems fair.
There must be something about Number Two's underwings that doesn't appeal So he comes over to where the action is.
The females don't know which way to turn.
But Number 0ne won't allow anyone else on his pitch for long.
There's not room on this part of the tundra for two.
So competing for mates only too often leads to physical violence.
Scotland.
Here in the pine forests of the Highlands, fights between males are among the most violent of all.
The capercaillie is the biggest of grouse.
The arenas on which the males display are vigorously contested, and the best, in the end, is claimed by the most powerful male, who will defend it against any intruder.
He is so charged up, this being the breeding season, that he will display to almost anything, including me.
Now, now.
Now, now.
But here's a really serious rival He is being very reckless indeed.
Birds can get very badly injured in battles like these and even die from their wounds, but the rewards they are fighting for are very great.
This is the most important moment of their year.
The females tour the duelling grounds to select the bonniest fighter of them all.
And they seem to agree on who the champion is.
Runners-up are almost universally rejected by the females, while the winner attracts almost more mates than he can deal with.
Some males make the job of the females in choosing between them easier by gathering together and displaying in groups.
And there is one bird in the canopy of the Brazilian rainforest here who has perhaps the oddest way of trying to impress the females.
It is called the Calfbird.
(DIN0F BIRDCALLS) They compete with calls.
The sound is greatly amplified by air-sacs on their throats.
The skin surrounding the sacs is so thin that, as they inflate, you can see right through them.
This assembly is a hundred feet above the ground, high in the canopy, so high that very few people have ever seen the birds performing this extraordinary chorus, let alone film it.
The top male, with, presumably, the best voice, occupies the best site - a forked branch totally free of leaves.
The females look exactly the same as the males, as you might expect since the males are not using special costumes to compete with one another.
When a female flies down to the best branch, all the males call with renewed intensity.
More females arrive.
A female tells the male she has chosen him by giving him a peck on the neck.
She flutters to the other branch invitingly.
But he is concentrating so hard on his display that he doesn't seem to notice her.
She tries again.
That's the idea.
And then he notices a second female.
Call as they might, none of the males on other branches get a look in.
The Calfbird has a cousin whose males also display in groups.
They compete not with sound but with colour.
The cock of the rock.
The males assemble in groups of a dozen or so, perching low down on lianas, watching out for females and squabbling among themselves.
The female is dull-coloured.
She has no use for bright feathers.
Her arrival beside the display ground has an immediate effect.
The males flop down.
Each one owns a particular patch of ground, his court, on which he, and he alone, displays.
Each now has the problem of how to persuade her to land beside him, and a cock of the rock's idea for doing that is to bounce competitively.
They adjust their positions slightly to try and stay in a patch of sunshine if they possibly can.
0nce again, a peck on the neck says ''I'm yours''.
And once again, the male is not very quick on the uptake.
But he gets there eventually.
After this is over, she will go off and rear her chicks by herself.
Another female.
She makes exactly the same selection.
By gathering together, the males make sure that the females know where the marriage market is, but the price of doing so is that only one or two males will make a sale.
In just a few species, however, the males in a neighbourhood don't compete with one another, but collaborate to form a team.
This is the blue manakin.
He is the captain of his team and he whistles to summon the other members.
The team is complete and the show begins.
They are striving to prove that they are the best team of acrobats in the neighbourhood.
A female arrives.
She is going to get a close-up view of the performance from the actual dancing perch.
If she is sufficiently impressed, she will mate with the captain.
But why should the assistants help him? Because if something happens to the captain, one of them will have the chance to inherit his position.
It may not be a large chance, but it is better than performing solo and having no chance at all.
That's enough to show how expert they are, so the captain dismisses his assistants with another special call.
If the lady decides to accept him, she will mate with him nearby.
She will then fly away and he willjust keep on dancing, hoping for another success.
He will never knowingly see his offspring.
But not all polygamous birds are so neglectful of their parental duties.
Here on the pampas of Argentina lives another male with many wives who takes his nursery duties very seriously indeed.
These eggs are all looked after by one single male.
And even now he is trying to entice another female to come here and add another egg to this huge clutch.
He's a Rhea, a South American ostrich, and he's mating with one of the group he has managed to attract into his territory.
Tomorrow she will lay.
The whole party now moves towards his nest.
He settles down to continue incubating.
And one of the females with whom he mated yesterday is now ready to lay.
She settles down within a yard or so of the nest.
An egg is on its way.
She leaves, and he rolls her egg into the nest to join the rest of his collection contributed by his other wives.
He may accumulate as many as forty of them.
Because the male has taken total charge of the nest, the females can be just as promiscuous as he is, and that female, having laid here, will now be going away to find another male with another nest to see if he will accept another egg.
That's unusual behaviour for a male, taking total responsibility for incubation and for chick rearing.
0n the tundra of the Arctic, however, another species has taken this reversal of roles further still.
These are red phalaropes.
In almost any other species, you would be right to think that the bird with the brighter markings on its head and neck is the male.
And that judgment will be reinforced when you see two brighter birds fighting in front of a duller coloured one.
That's typical male behaviour.
But the truth becomes apparent when you see them mating.
It's the duller coloured one who mounts on the other's back.
It's the duller one who is the male.
That is the female.
He now goes away to the nest that he has already built.
The brighter coloured female comes back to him for several days thereafter, to mate again and to add more eggs to the nest.
While she sits, he stands aside.
Now it will be up to him, and him alone, to incubate the eggs and look after the chicks.
No one really understands why the phalaropes, almost alone among birds, have reversed the role of the sexes.
But mating openly with multiple partners is the exception.
In most species, both male and female are needed to bring up the young, so most birds after mating stay together as a pair, at least during the breeding season.
An indication that this is the basis of their relationship is that the sexes are broadly similar in appearance.
But even so, living as a pair doesn't preclude a little infidelity, now and then.
Perhaps the most bizarre behaviour of all takes place in the suburban gardens of England, and it seems that until very recently, nobody even noticed.
A young female hedge-sparrow, a dunnock, ready to lay.
This is her mate, Alpha, singing lustily, declaring his ownership of the nest and the territory around it from which he gathers food.
The pair often feed together, a devoted couple if ever you saw one.
He seldom lets her out of his sight, for she is not as faithful as she might be.
There's a third bird around - Beta, another, younger male.
He's not popular with Alpha and they're continually squabbling.
Sometimes the fights can get quite vicious and feathers fly.
But in spite of that, Beta stays around, skulking in the hedge.
Alpha, it seems, has the female to himself once more.
But she has got her eye cocked.
Beta is still in the hedge, calling quietly to her.
She joins him, and now, while Alpha is preoccupied with feeding, she and Beta get together.
Twirling her tail is an invitation, and in a split second they mate.
Beta flies away.
But now, out in the open, she is courting Alpha with that same old tail twirling.
He takes precautions to ensure his paternity.
He pecks her genital opening.
And she eventually ejects a droplet.
It's Beta's sperm.
He persists for up to two minutes until his rival's sperm is all gone.
And now he mates with her.
It will be his sperm that will fertilise her eggs.
She has kept two males happy, both of whom will help to feed the young when they hatch, and Alpha has managed to ensure that he will be the father of the eggs she will soon lay, or, at any rate, most of them.
But it is here in the south east woodlands of Australia that infidelity reaches its most astounding, indeed, you might think, its ultimate height.
And it occurs among the families of this dazzling little bird the superb fairy wren.
He is an attentive male, courting his female with little gifts of food.
But there are other males around, identifiable by the different rings on their legs.
0ne of them dances for her, flaring the blue fans on his cheeks.
Yet another male is also flirting with her.
And here's another.
And she selects one of them.
But her first, established male, is not around to see all this.
He is visiting a female neighbour, and what is more, he's carrying a bouquet, a flower petal, something he never does at home.
And his flashy courtship behaviour pays off, too.
Now he is back beside his own nest and with his first mate, looking after the chicks that the nest now contains.
So the female fairy wren chooses the flashiest males to father her chicks, and allows her partner only just enough matings to ensure he helps to feed the family.
And the males, while they may have chicks in as many as six nests around here, may not have a single one in the nest that they actually tend.
They say it is a wise child that knows its own father, but that is never more true than in the bird world.
But extreme infidelity, like polygamy, is not widespread among birds.
Among swans, as amongst most birds, male and female stay together.
And by a combination of bonding with one another and driving away any who try to interfere with the partnership, they stay together.
Male and female conduct their courtship on equal terms, and when they are convinced they are compatible, they work together to build a nest.
Protected on most sides by water, and with a strong and aggressive mate to see off intruders, these swans will probably hatch their egg successfully.
But for many birds, they are now entering on the most difficult part of their lives.
They will have to employ all kind of ingenious stratagems if they are to raise a family, as we will see in the next programme in The Life of Birds.