The Secret Life of Birds

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Hello, I'm Robert Eddie.

And I'm Brian Cox.

Today's show is biological.

So first we have to lure Brian in by making it appear to be about physics because he's not really keen on living things or anything which have too complicated a structure or indeed an inner world.

Even in a quantum universe, subatomic particles are more predictable than magpies magpies and otters.

And

he doesn't like anything that can't be explained in a one-line equation.

It's going to get complaints now.

People are going to be writing, and why do you hate magpies and otters?

I don't even know what a magpie or otter is.

I know they're made of muons and gluons, but after that, I lose all interest.

I have genuinely never met a human that smiles so much when he says the words, and eventually the heat death of the universe.

Oh, won't that be neater?

Well, it won't actually, will it?

Because the heat death of the universe is a state of maximum entropy, so it'll be more disordered.

So it'll be very unneat.

It's a definition, the definition of the heat death, isn't it?

It's the most highly disordered state.

So, anyway, today

we'll be talking about bird behaviour.

Genuinely,

so just to lure you into bird behaviour, I can tell you now that research into European robins suggests that they may maintain quantum entanglement in their eyes for the purposes of navigation.

They're using this quantum effect to visualize the Earth's magnetic field.

Quantum.

Happy?

Well, not really, because you're not a European robin anymore, are you?

Well.

Anyway, we're not talking about quantum entanglement.

We're going to be talking about the secret life, by which we actually mean the sex life of of birds, but we have to call it secret life'cause that's uh radio times gets a little bit anyway.

So

to enlighten us on the lurid ornithological possibilities of nature, we have a zoologist, a naturalist, and our regular theologian who has recently taken an interest in parrots.

And they are.

I'm Tim Burkhead, I'm a professor of zoology at the University of Sheffield.

I wrote a book called Bird Sense and I've just finished a book on the pioneering ornithologist Francis Willoughby.

And the thing that really amazes me about bird behaviour is the issue of whether they feel and can express their emotions.

My name is Steve Baxhall.

I'm a wildlife television presenter.

And the thing that intrigues me about bird behaviour is the murmurations of starlings, the remarkable flocking behaviour that they undertake before roosting in the afternoon, evening.

And it's like a billowing smoke cloud in the sky.

And I still don't know how they do it and why.

I'm Katie Brand.

I'm a writer, actor, comedian, and amateur theologian and the thing that most intrigues me about bird behavior is how they judge so accurately the massive distances they cover during migration.

And this is our panel.

Now, can I just throw this out to the whole panel though?

Is there a better word than murmuration?

Murmuration is one of the most beautiful words to behave.

It is magnificent.

So you're already through to round two.

Oh, it's not how the rules work.

As Robin said in the introduction, we do a lot of physics on this programme.

Physics, definitions are important in physics.

So can we start with a definition?

What is a bird?

A bird is a dinosaur.

Recent discovery is that birds are not distinct from reptiles, they're just part of that dinosaur lineage.

And it's well known now that lots and lots of dinosaurs had feathers even before flight was essential.

So, basically, a bird is a dinosaur.

So, would all birds have one common dinosaur ancestor?

Do they all go back to some sort of mitochondrial Eve dinosaur?

They're in a group called the theropods.

They're in essentially the same group as T-Rex was.

That's what I'm getting at.

All birds are related to the T-Rex.

Could that be the case?

Essentially, yes.

In fact, most modern taxonomists talk about dinosaurs and non-avian dinosaurs being all the things that we would think of as being dinosaurs.

Everything from you know the uh the the brachiosaurs to the velociraptors to uh diplodiplodocus all of which are non-avian dinosaurs it's interesting because you you both reacted when i said so birds are descended from dinosaurs which is that you both would say no they are it's one of those things like like people say you know we are descended from chimpanzees we're not we share a common ancestor with chimpanzees and it's the same with with birds and dinosaurs it's not correct to say that they are descended from dinosaurs they are dinosaurs Yes.

Now, in fact, we're going to just move on quickly.

We're slightly going to change the order of what we're going to do because very often we have big, egotistical guests on this show who get agitated if they're not introduced on time.

And this is one of those examples.

Please welcome tonight's guest Raven, but quietly.

This is

also

introduced Lloyd Buck.

Lloyd, this is his wonderful Raven Brown.

And we're going to.

That's the name of the raven, by the way.

It's not a raven bran,

very strange way of saying it.

It's one of my favourite cereals.

For the benefit of those listening, Bran is currently ripping large chunks of raw flesh from Lloyd's glove and just momentarily escaped for a minute just now.

So I should say for the radio listeners that Bran is quite large.

Although, Lloyd, you said he was a to me, he looks very large from about a foot away from my hat.

But you said he's an average size raven, not particularly large.

No, he's just your average normal size raven that you'd see anywhere in the wild, all over the northern hemisphere.

And

we're going to talk about intelligence in birds, but you were telling some stories about how clever he is, and you've known him all his life, so he's

11 years, is it?

He's seven.

Seven years.

And you also said he might live...

I was amazed about ravens, 40 to 50 years lifespan.

In captivity, yes, they can live an awful long time.

So he could potentially outlive me, you see.

So, hold on, no, I don't want him to change.

I'm wearing some quite large hoop earrings, which I'm just going to take off.

Bran flew very close to Steve's head that's a little bit more difficult.

Bran and I are old friends.

We first worked together when he was just a few months old, and it's always been working through elements of avian problem solving.

And so, what I've got alongside me here is what looks like the world's worst fish tank.

It's kind of this perspex box, and in it is a food reward.

But what Bran's going to have to figure out is how to get at it.

And to begin with, you know, obviously what he's doing is just pure and simple trying to get through the perspex.

He can see it and he's trying to get at it.

But he's going to have to figure out the way of doing it because there's only one way this problem can be solved.

And he's already got straight to the heart of the matter, which is that there is one weakness in this box.

It's this kind of cover of paper here, which he's just with surgical precision removed.

But now he cannot get at the food.

It's at the other end of the box, so he's going gonna have to pull it through using this string

and in a matter of seconds he's solved the problem and he's he's eating it which is the audience all want to clap but we told them they can't

remarkable thing but it is absolutely fascinating watching birds going through tests like this and and i've seen this many many times it seems like to begin with there is a period of experimentation where they're just trying out lots of different things to try and figure out how to get to the food and he's now hopping around all over the place.

He's now working out which member of the audience looks most delicious.

He's had to be tempted back.

It's a fascinating thing as well, Lloyd, because you were saying about the intelligence that there are some things that say a cockatoo may be able to do that a raven can't, but that doesn't necessarily a cockatoo is not smarter than a raven.

Is that right?

No, I think it's generally thought, I think Tim would agree with this, that ravens have the broadest problem-solving abilities

of any bird, I do believe,

in their ability to problem-solve.

Can you give us an example of his behaviour?

Well, it's like I would describe him as having a child with ADHD for life.

He never gets out, never grows up.

And so obviously

he's very curious, he's very bonded with me.

So we go out for our fly every day.

you know and he loves it he's like a flying dog really and but the trouble with that is you see he's much cleverer than i am so he is always working me out so he knows for instance here's my flying pouch the reason there's a zip bit there is because that's where all the food is now with all the birds of prey that we fly at home you don't have to worry you don't have to have a zip because they'd never raid you but Bran knows exactly if I leave that unzipped you see I'll have it around there like that and we'll go out and he'll be off flying and then he can't I'll call him for some food and he'll notice maybe as he goes off again that I forgot to zip it up but he'll know I'm concentrating then so he won't try and raid me because you know I'll stop him but then maybe my phone will will go, my mobile.

So I'm on there, I'm walking along the phone, I'm not concentrating.

He spots this, so he'll come round behind me, and the next thing I know, I've got this raven sliding down my shoulder,

straight in, food gone, bomb.

So that's one of his classic little ways of raiding me.

Another thing is when we clean him out in his avery every day, he's got a big travel dog cage that he travels in.

I pop him in there so he's not pecking the bristles off the broom and generally getting in the way.

So he waits patiently.

And then at the end, I undo the and put food food out, let him out.

But a couple of times in the past, I forgot to do that for a while, and then I thought, oh, I left Bran in his travel case, I've gone and let him out.

Oh, sorry, Bran.

So now, what he does often, he'll sit in there with the door shut, even though I let him go, and then he knows that he could trick me because sometimes I think, oh, I didn't let Bran out.

When I go in with the food to say sorry, he bursts out, and I say, Oh, I tricked you.

So he'll deliberately put himself in his travel cage and sit there, like looking, oh, look, you've left me there again.

Do you find by trial and error that there are different forms of luck which will eventually be worked out in terms of these kind of moments of

great scale?

Well, I mean, I'll just.

Oh, yeah, you've done it.

He had a very good luck at robbing that night.

Just

get away with that.

They're all as different in characters, I would say, the birds, as you or I, and especially with the COVIDs.

So, Bran has a particular type of problem solving that appeals to him.

So, what appeals to him is this kind of thing, where he's got to work out how to break into something, put in strings, undoing things.

He likes that.

So he is smarter than,

you know, when you think of the main domesticated pets, we have cats and dogs.

I mean, in terms of the ability to learn and to experiment, I presume superior intellect.

I would argue that.

Yes, I would think that personally.

I think he is.

And he would

give you an idea.

The first time he was ever presented with this, he hasn't seen this problem problem for nearly three to four years, and he only saw it once then.

And I presented it to him, and I didn't show him initially.

I didn't want to show him how to solve it.

And it took him, I think, probably about 30 seconds to work out how to solve it.

That's what makes Corvids so special: that you can give them a completely novel problem and they somehow work it out.

I'm just going back to what Lloyd was saying: Corvids live in a particular kind of environment, and

the kind of searching behavior and the inquisitiveness that you've just described, that's kind of that reflects the environment in which they live.

Parrots are also incredibly clever, but they live in a very different environment, and they would be clever in very different kinds of ways.

We've done tests like this.

Corvids are the ones that the crow family that are best known for having, you know, really intelligent kind of appearance to them.

But we've done tests with kias, alpine parrots in New Zealand, and also with a bird called the striated caracara in the Falklands.

And we took in these tests, which they'd never seen before, which were perspex tubes with a food reward at the top.

And the only way they could get at it was to operate a series of different levers, and the food reward would be presented at the bottom.

And the first time that you place it out, first of all, these birds are following me around everywhere.

They're bird of prey, they're quite menacing looking, it's like something out of Hitchcock's the birds.

And the first time you put down this

perspex tube, it's very much like Brown did there.

They peck at it, they pull at everything, and eventually, after about 10 minutes, by pure chance, the food reward falls out.

The intriguing thing is what happens when you put it back a second time because the second time they do the whole maneuver in about two minutes and the third time you put it out they solve it instantaneously.

So it's not necessarily that they're figuring out how to do it from the start, that they're solving this problem going, oh, I need to twist that and the other, but they remember the way that they solved it the first time around.

And now we have

another demonstration for Bran to do, which is to do with language and to do with seeking out things.

So I can't say the word that he's going to do, but it's not.

I feel like I should cover up the fact it's been written in case it's

what we have is we have a S-T-O-N-E, an S-T-O-N-E, and we're going to put it somewhere around, we don't let him see where it is, and then we're going to let him search for it, and then you will say the word to him, and he will understand what that is, and he will go and he will look for it, and he will find it.

Hold on, hold on.

So, we've got the S-T-O-N-E.

I'll say this to you.

Which seems to be very close to the K-A-T-Y at the moment.

The S-T-O-N-E is close to the K-A-T-Y.

Very close to her feet.

And so now Bran is going to come out and

we will say the word, he will know what he's searching for and then he will search for it.

Okay, we ready?

Yeah.

Come on, Bram.

He's a good boy.

Right then.

I hope he'll take me for dinner after this.

He will.

He will take you for dinner, yes.

So, and this will be a demonstration of how well he understands language and remembers what to do.

Where's your stone?

Where's your stone?

He's gone.

Right, so now he's literally gone.

And we should say one of the important things is that Bryn very,

sorry, rather, Lloyd very carefully didn't look in the direction of the stone.

So he was giving no verbal cue that in the way that before, when you've heard about certain creatures like counting horses and stuff, where there were various different.

Oh, well, that's that's everything blown off.

That's all right, but this is so much nicer than a goose.

This is nice.

He actually whispered

while he was down there, he whispered to me, Your shoes are very large.

All he said to me was, Never more, never more.

I thought, ah,

that is.

But it's a very.

Some of you will probably know sometimes ravens are called feathered apes.

And you watch, and it's not merely the intelligence, the kind of something about the movement and and the beauty.

There we are, so he's just he knows I'm getting that's by the way.

That's the little stone.

We were out flying one day, and he picked it up seven years ago and decided he liked it.

Don't know why he was playing around with it, so I thought I'll keep it.

And then I don't quite know how I come about to hide it and try that.

I can't even remember how it first came about, but I suddenly realized he would look for it.

And we've done an experiment where we put that on a whole pile of ag, oh, hold on, Brad.

I'm sorry, you got a bag, he thinks there's something in there for him to eat?

Brent,

he likes handbags.

He likes going in handbags.

Because he knows people often keep snacks, you see, in their bags.

So you think, oh, I can't look in there.

Our audience is the kind that often go out and buy offal shortly before a show.

This could go very wrong.

He is lovely.

He's a very sweet-natured raven.

He's really sweet-natured and friendly.

And they're like a lifelong companion, really.

You know, know, he's a huge time commitment, but he's worth it.

So, when you flew down there, obviously, you know, you want to make sure you know where he is, but if he could get out of the building, would is he domesticated to the extent or at least partnered with you to the extent that he wouldn't try and fly away or go to the Tower of London to see his cousins, or

he would find you and stick with you, or stay where he is until you found him?

We're a bonded pair, he knows obviously, I feed him as well, but we are, there's much more to ravens than just the food.

But

yeah, I mean, he's lovely.

We go out for a fly and our walk, and he just enjoys flying.

And ravens are unusual, I think, for birds because sometimes I think they just do things because it's fun and

because they can.

They don't necessarily always do things, I don't think, for a particular reason.

I think they sometimes do things because they just can do it.

But playing is meant to be a hallmark of an intelligent animal, isn't it?

Like dolphins play, and is that true?

Sort of.

I mean, people really don't understand play at all.

People say that.

And corbirds do play probably more than any other bird.

I've watched magpies snowbathing.

Have you seen this?

Yes.

On their backs, sliding down, just as though they're tobogganing.

They do.

They clearly enjoy it.

So I think there's something in that.

Well, we should.

Yes,

those of you who know the British Sign Language applause, go for that because I know some people down the front did that.

So thank you very much, Lloyd, and thank you very much, Brilliant.

That was absolutely fascinating.

That's brilliant.

Thank you.

This is what I love, really making the Radio 4 listener work with their imagination.

Well, I thought, I mean, just to sum up, I mean,

there's clear intelligence there, problem-solving, understanding language.

He mimics as well.

Apparently, so

on the scale of other animal intelligences that we know of,

where would you place the most intelligent birds?

In the last decade or so, there's been a resurgence in trying to understand bird intelligence.

And the people that study corvids in particular, but also parrots, have kind of tried to raise their profile.

So they're regarded by a lot of people as being on a par with chimpanzees.

And as I say, it's corvids and parrots.

And if you look at their relative brain size, they have relatively large brains.

But I think it's easy to deceive yourself.

I studied bullfinches, which is kind of the antithesis of bran, a little songbird, and they also have tremendous intelligence.

They also have a very big brain.

But their intelligence manifests itself in another way.

Like ravens, corvids, and parrots, bullfinches form very long-term, rigorous pair bonds with their partners.

And I think what happens

when people have kept bullfinches in captivity, they can train them to sing fantastically complex tunes.

And I think what's happening there is that, just like Bran, the bullfinch is imprinted onto its owner, and they particularly like men for some reason, and they're using that bit of the brain that would normally be used for maintaining the pair bond in order to learn these complex songs.

And maintaining a pair bond is actually something quite complicated because you have to be able to anticipate what your partner's going to do.

And so there seems to be fairly strong evidence across a range of animals that when you have a long-term pair bond, you need a lot of cognitive power.

What's the most intellectually disappointing bird?

Because

I always say, you know, no one's a big fan of pigeons generally, are they?

No one's keen.

I mean,

is there one bird where just when you think, oh, we're really finding out all these credits, oh no, that is a disappointment.

pigeons pigeons are nothing like as dumb as they're made out of exactly the guillemot that i've studied for 45 years used to be called the foolish guillemot and and that's because when they're faced with a predator be it a raven or a gull or a human being they sit tight on their egg or chick because that's their strategy that works for ravens and gulls but it doesn't work for humans but for humans it was easy because you could just go and pick them up and either kill the bird or take the egg but they're anything but stupid in fact there's probably no bird that's really stupid.

Oh, chickens are stupid.

No, chickens are in no.

Let me give you an example.

If they were so stupid,

let me give you an example of how smart chickens are.

We did some experiments and we were interested in the mating behaviour, of course.

And I discovered that if you very gently held a hen in your fingers and lay on the ground and pointed the hen's bottom towards a cockerel, he would go, whoa, fantastic, and jump on her and mate with her.

And then we fitted the female with a kind of chastity belt that we could collect the sperm, which is the kind of stuff that biologists do.

And

we wanted to know how many sperm a cockerel could transfer to a female.

And so what we did was we put the female behind our back and the cockrel would wander around, we'd put her out again and he'd come and mate and we'd collect the sperm and we'd count them.

And then after a bit we swapped the hen.

So it was a different hen.

And he suddenly just started transferring many, many more sperm.

And we did it again and again.

And then we noticed what he did was every time, before he mated, he had a quick look at her face.

And they go, oh, it's you, love.

I'm not going to bother.

If it gave him a new one, he goes, woohoo!

And we did it time and time again.

They are super smart.

Plain boy chicken.

I'm just radically rethinking what I think of as smart behaviour now

in relation to the pub on a Friday night.

Did you know, actually?

the facts in research in this programme, we found a fact that the 2003 Ignobile Prize for Biology was awarded to the first recorded case of homosexual necrophilia in the Mallard duck.

Now, I was going to ask about this because I have seen ducks where I live doing it, and it is the most extraordinarily violent and distressing thing I've ever seen.

I felt the need to intervene at times just for the poor female duck.

Is the female duck hating it as much?

I mean, it looks appalling.

It is appalling.

And sometimes females get drowned because most of the copulations take place on the water.

But therein lies what I think is probably the most fascinating story about bird sex you're ever going to hear.

So in lots of.

Lay it on me.

In lots of duck species.

The male has a penis.

Not many bird species have a penis, but the male duck has a penis.

And the mallard is the one that you will all have seen.

The duck, but not the penis.

And the penis is the most remarkable structure.

It's completely unlike a human penis.

And it's a spiral structure and it's folded away in a little pouch inside the cloaca near the vent and it's erected by lymph rather than blood.

And it's an explosive device so that when the male comes in contact with the female, bam, this thing goes off and it spirals its way up the female's reproductive tract.

Now, because males have got a penis, they can force matings onto females.

And so it's called forced extrabear mating, basically rape.

And, oh my gosh,

different species of ducks have different sized penises.

And a few years ago, a paper was published in Nature about the Argentine lake duck.

And the duck is about this long, it's about a foot long, and its penis is about 18 inches long.

And all the text in the paper was about what the male might do with this enormous structure.

And because it was to do with sperm competition, we thought, well, maybe he uses it to remove sperm from previous matings.

And everything was male-orientated.

And I said, actually, what happens to the poral female?

Where does all that penis go?

So we started a study to look at this.

And we looked at the anatomy of the female's vagina by picking up roadkill.

Birds in the spring are killed and huge numbers on the road and you can dissect them.

And so we dissected this and female ducks and my postdoc said to me, I think you better come and have a look at this.

There's something a bit weird about this.

So every previous bird vagina I'd looked at was just a straight tube.

This one had a little side branch and a bit of a spiral structure.

To cut a long story short, short, we looked at a lot of different duck species.

And the duck species that have the longest penis, the females have the most complex vagina.

And in the most complex situation, there are three side branches and a very rigorous spiral.

Now, I mentioned that the male's penis is also spiraled.

The female's vagina spirals in the opposite direction.

You could not devise a better way to stop a male in its tracks.

And what I imagine happens is that when the female is forcibly mated by a male she doesn't want, all she has to do is to clench her oviduct and the spiral titans and he's sent off down one of these blind alleys where he can't do much trouble.

I'm never taking my three-year-old son to the village duck pond again.

This is going to be a very interesting show to see which parts of it end up in the bit that

goes out during the school run and which goes out in the podcast version.

Can you better that story about

bird mating?

Do you know what?

I'd actually rather you didn't because I'd want something.

Otherwise half this show is just going to rehap to the sound of various different bird-life calls.

It's quite tricky because, actually, the majority of birds don't have a penis.

In fact, they just have a cloaca.

And most mating is what's called cloaca kissing, where the two cloaca come together, can be very, very brief, and there isn't this extraordinary, elongated penis that you get in the Argentinian lake duck.

But one of the most incredible things is that some of the birds that we see in our gardens all the time that appear to be the most common, the least sort of interesting of all, have the most extraordinary sex lives.

And one of those would be the Dunnock, a bird which is a real common garden visitor here in the UK and is an absolute deviant.

I mean they come up to the mating season.

It's a deviant, but it's just enjoying life.

Yeah, no, it's not judged them.

That's fair.

It's not judged them.

Well, except for the fact that coming up to breeding, the male's testes swell to about 8% of its body weight, which would kind of be like me having testes the size of a sack of potatoes.

And then they will mate 30 plus times in the middle of the day.

I know some of that laugh there comes from people.

People just remembering some of the trousers you wore in Strictly Come Dancing.

See if there were any clues as to what time of year.

No, I think you're fine.

With multiple different partners.

There are some birds that

their nests have been examined, and 98% of those nests contain eggs from different parents.

And birds that may appear to be monogamous actually are are really sneaky and a bit dodgy.

Female birds, don't they?

They try and sort of keep all three or four males guessing as to who might be the parents.

So we studied a bird called the vasa parrot, which is probably the world's ugliest bird.

It's a very big black parrot, but its main claim to fame is that the male has what we call the cloacal protuberance.

And it's about the parrot's about 18 inches long, and this structure is about the size of a tennis ball.

And a colleague of mine, who was the curator of birds at Chester Zoo, phoned me up one day and he said, I think you ought to come over here and have a look at our vasa parrots.

They're mating at the moment.

And as Stephen said, most copulating birds takes about two seconds.

These vasa parrots were stuck together for half an hour, and the male inserts this structure into the female and actually forms what's called a copulatory tie, just as in dogs.

And they sit side by side.

He's presumably whispering sweet nothings in her ear.

She's eating Jaffacake.

Have I given too much away?

Have I opened the book a bit too wide there, I think, maybe?

And we thought, you know, okay, this is fantastic.

My guess is that this must be something to do with sperm competition.

Nobody knew anything about avasa parrots in the wild.

We went to Madagascar, did a study, and sure enough, it is the most remarkable avian mating system.

The females own the nest, it's a hole in a tree.

She comes out, sits on the top of another tree, and sings.

Not many female birds sing.

She sings, and males fall out of the sky to form a cue to copulate with her.

her.

And lots of them copulate with her.

And then, when we did the DNA fingerprinting on the chicks, every egg has got a different dad.

And they all bring food.

Yeah, and they all bring food.

Yeah, exactly.

That's precisely that.

So, is most of what we see, Steve, in terms of what we interpret as beauty within birds, you know, whether it may well be the dawn chorus, whether it is plumage, all of it pretty much down to some level of sexual selection.

Very much so.

So, the norm amongst birds is for the male to be the most ornamented.

There are exceptions to that, but generally speaking, the male solicits the attention of the female, and that can be in the most extraordinarily dramatic ways you can imagine.

From the bowers of the bower birds in New Guinea and Australia, which are these,

they're part of what Richard Dawkins referred to as the extended phenotype.

They're an extra part to the character of this bird, which is not a nest, it's a construction that's that's created to attract the attention of female birds.

And I've been lucky enough to be wandering through the forests of New Guinea, and you'll see what looks like a lattice work igloo with an array of different beautiful objects laid out in front of it, which the bird has selected to make it more beautiful.

I've even been to particular bowers in Australia where, in place of natural objects of beauty, this particular bower bird had discovered some poor child's toy plastic soldiers.

So in amongst all of the bulbs and the beautiful beetle casings were a whole bunch of little plastic soldiers.

There's one called the satin bower bird which erects a beautiful bower with an avenue running down the centre of it and then in front of it puts out all these beautiful blue items and they would usually be blue petals from flowers for example.

Now they're filled with you know blue plastic biro tops and plastic straws and things and you can sit in front of the bower and remove something blue and replace it with something red and the adult bird, the male bird will fly down and caw in your face and rip out the blue thing and throw it the red thing and throw it away so that his perfect structure is there in place to attract the female.

This is in terms of the cost of this.

I was thinking of

the peacock, obviously, is one of the most, and Charles Darwin, I can't remember if it's in one of his books, whether it was in his journals, where he talked about the sight of the feather in a peacock's tail makes me sick.

And he felt, you know,

the burden, the evolutionary cost of having this enormous tail, you know, was was almost an unbearable level of evolutionary cost.

He had grappled with the topic of sexual selection for so long.

I think that's why the peacock's tail made him sick.

But there is, you have touched on a really significant point there.

So the female prefers a male with a long tail.

Let's say it's peacocks, okay?

And if you were to give a female a choice between a male with a two-metre tail or a three-metre tail, she'd probably go for the guy with the three-metre tail.

The problem is that with a three-metre tail, you can't fly and you'd be eaten by tigers.

So sexual selection drives traits like the bower

or the peacock's tail up to the point where natural selection kicks in, and then natural selection says, Well, that's enough.

And so, that's why there's a kind of limit.

But that experiment has been done, hasn't it, with widow birds?

So, widow birds are these birds which are not particularly dramatic-looking, apart from the fact that the male drags behind him this ludicrous plume of tail, which can be half a meter long, and obviously is

to its detriment.

It makes it much easier for predators to find, it makes it harder for it to fly.

But by adding extra parts onto the tails of widow birds, those males were preferentially selected by the female.

So it's clear that they prefer males that have this extra ornamentation.

And in the 70s, an Israeli biologist called Amot Sahabi came up with a very elegant idea called the handicap principle to explain this and the idea of honest signaling, which is down to the idea that if a male can demonstrate its fitness in a way that cannot be faked, that cannot be be in any way not real, then the female has more reason to believe that he has strong genes.

So by having something that is a deliberate handicap that makes it harder for that bird to reach maturity, harder for it to breed, it's therefore saying that its genetic material is strong.

And that is a very elegant explanation for why you have things like the tail of the widowbird and the tail of the peacock.

And that relates to Robin's point.

I mean, the trait has to be costly, up to a point, because if everybody could fake it, they would.

In terms of the social behaviour, so for example, penguins are often held up as this sort of paragon of virtue.

They mate for life and they have...

Swans, I think, would be a better paragon of virtue.

Well, so

is that

it's true in some birds, but not others.

How complex is the social mating behaviour of the family?

Okay, Steve alluded to this earlier.

Most birds are what we call now socially monogamous, which means that they breed as pairs.

Not all, but 90-odd percent of them breed as pairs.

And we now, as a result of DNA fingerprinting, we have to distinguish between social monogamy and sexual monogamy.

So there are very few birds that are truly sexually monogamous, and the mutes one is one.

Penguins aren't, I'm afraid.

Puffins.

We don't really know about puffins, but probably not.

Yeah, everybody thinks puffins are cute.

They're boring.

Come on.

Yeah, they're probably not absolutely faithful, probably a bit like Guillemots.

So in Gillemotts, for example,

about 7% of offspring are fathered by the chap next door.

But in the blue tits that you might have breeding in your garden, it could be 12%.

In reed buntings, it's about 70%.

And nobody really, really understands that.

Now, the benefits for males are really clear because if you're paired to one female and you can make sure you father all her offspring and then go next door and father somebody else's offspring, you've increased your reproductive success.

That's what's going to, and that promiscuous behavior is what's going to get those genes into subsequent generations.

But the $64,000 question is: why do females go for this?

So maybe you can give us some insights.

Why do females go for what?

Why do they have extra pair matings?

There's no benefit that we can think of that females get.

From mating with multiple partners.

Well, from mating with

a partner over and above the regular partner.

I don't, well, I guess it's because you only get

the egg is more precious than the sperm, isn't it?

There's fewer eggs in the world than sperm, and so you would want the best sperm to reach your egg.

Okay, so that's that's been one of the explanations for why females seek extrapair matings.

And there's now a handful of studies that have gone on for long enough and in enough detail to check whether the survival rate of the offspring fathered by the extrapair male are fitter in some way.

Do they live longer?

Do they have high reproductive success?

And they don't seem to, which is really disappointing because that was our best explanation for why females engaged in these extrapair matings.

But if you've got two males and you've got a child, then, and neither male is sure

whether the child is going to be able to get away from the middle of the

double the support.

Well, in most birds, after the extrapair mating, you can't.

Oh, we're talking about birds.

Sorry, I was as if.

Well, it would be true.

But again, the example that Steve mentioned, the dunnock, so their system is very interesting, very odd.

So the female often pairs with two males, and each male wants to be the father.

This is from an evolutionary point of view, he wants to be the father of all the offspring.

So he tries to keep the other male away.

So they're always battling.

And then when they get the female on their own, they're copulating like mad.

And the female, on the other hand, wants both males to mate with her, because if both males mate with her, both of them will help rear the chicks.

And if that happens, she can rear an extra chick.

So it's a wonderful example of the battle of the sexes.

So the two males are competing like crazy, and the female wants both of them to mate with her.

I think, you know, we're kind of obviously the the whole idea, this wonderful, idealised idea of bird monogamy that we have, thinking of the swans that mate for life, it is slightly idealised.

But there are also examples of birds that have an extraordinary relationship that lasts for many years, for many decades.

The albatross, for example, you know, I've been lucky enough to sit alongside the nests of wandering albatross on Bird Island, South Georgia, and alongside the exact same nest that Sir David Attenborough filmed alongside in Life of Birds, situated in the exact same location.

The same birds coming together over many decades.

They'll go out to sea and not see another bird of their own species probably for over a year.

And when they return and come back together, they go through this glorious dance together.

And a lot of that is ritualized movement, so it's probably sort of showing how fit they are.

They're extending their wings to show their size and their ability to be able to fly.

They peck each other's beaks, which is probably in some way symbolic of the ability to be able to return food to the chick.

But this will go on throughout their lifetimes unless one of them dies, in which case they will find another mate.

And there are so many examples of that throughout the bird world.

There aren't in the mammal world.

You know, as Tim said there, it's you know, about 90% of bird species or more have this monogamy throughout the breeding season, at least apparently.

In mammals, that's almost exactly polarised.

So about 90% of mammals are polyandrous or polygamous.

Is that because the mammal offspring are born quite capable, or they become quite capable quite soon.

And because they, some theories with humans, isn't it?

Is that because babies are born so helpless, because the heads have evolved quicker than the size of a woman's pelvis, is that right?

That there's a kind of this idea of love is a way of bonding humans for the length of time it takes for a human baby to be able to stand on its own feet and eat.

So, but you could say that about chicks, couldn't you, and eggs?

That there's a delicate, there's a long period where a chick is quite helpless.

So it helps to have have some form of ritual which keeps the pair together.

Yeah, that's probably true, and that period is extended depending on what skills that chick is going to need to live its life.

So a harpy eagle chick might spend 12 months branching next to the nest that it's hatched in because its method of hunting is so complex and it probably has so much that it needs to learn.

It's very difficult to prove that that is directly connected to certain parentage because

bird parents will still look after young that are not their own.

They'll look after young of a totally different species.

Brood parasitism, cuckoos that we have in this country will be looked after by bird species where the adult bird is half the size of the cuckoo chick that they're rearing.

Once they've imprinted on a chick, it doesn't matter if it's theirs or not.

So it's very difficult to prove a connection between those two things.

The difference between birds and mammals that is key here is that in mammals the female suckles the offspring, so the male can just swan off to mix metaphors.

Whereas in in in a lot of birds, in monogamous birds, it takes two parents, in particular in the case of an albatross, it takes two parents to rear one chick.

Ken, we we've heard um the this remarkable descriptions of the the variety of behaviour, we've seen some of the behaviour with the the raven, remarkable behaviour.

To to go back to your initial statement about birds and and feelings that you said you'd like to know, I mean, just to draw this to a close, what would be your guess?

I mean, how do we characterize how

I suppose whether there is an internal, some kind of internal monologue there in birds?

It's a very difficult question.

It's such a difficult question.

That's one reason why it hasn't been studied.

I've taught animal behaviour to first-year undergraduates for more years than I care to remember, and I'm constantly frustrated by the fact that academics kind of work within a very narrow rut.

You know, there are certain things that it's legitimate to study, there are certain things that we wouldn't touch.

And early on, when Nico Tinbergen, who founded the study of animal behavior, he said, we don't do animal emotions.

That's too complicated, it's too subjective.

Luckily now, things are changing slightly.

And you only have to have kept a dog or a raven to realize that these animals do have emotions, they have personalities.

And it's it's only in the last few years that we've been brave enough to say okay let's accept this and then devise ways in which we can study it but it's still

I was talking to Lloyd before we came on

his raven definitely has emotional responses but it's they're difficult things to measure and to quantify in a scientifically rigorous way.

I know that sounds very boring but that but that's the fact.

About 10 years ago I was chatting to Bill Oddy about this and he was talking about the fact that blackbirds have a variety of different songs songs and one of which is a specific morning song if they lose their youngsters.

And I kind of nodded and went, that sounds like absolute tosh, Bill.

And then early this year, in spring, I was cycling down a country lane near my house, and a crow flew out of a bush with a fledgling, which it placed on the verge, and then it flew back into the bush and came back with another, placed it in line with it, flew back into the bush and came back.

and all three fledglings laid out in a row, it then killed them and flew away with them.

They were blackbird fledglings.

And I came back along that same lane a few hours later on, and coming out of the bush was the most mournful sub-song I've ever heard from a bird.

And it was a blackbird producing a specific song, which you can only, you know, no matter how scientific you want to be, take as being a parent grieving for its youngster.

And at that moment, you know, you cease being a scientist and you just feel a connection to an animal that you cannot fail but believe has emotions.

I'm not saying this is scientific, but I will say Bran before the show started took me to one side and said, if I wasn't already with someone,

I'd definitely be interested.

To be fair, I think he was mainly interested in your Jaffa cakes.

This is

well, well done, Sig, for making it this is a proper biology show because we've mainly done sex, but then it's ended with death.

So that's the way it should be, shouldn't it?

So we, as usual, asked our audience a question as well, and we asked them if you could teach a parrot one sentence, what would it be and why?

And

this one is, they would teach them billions and billions of stars.

Though it should actually be done as billions and billions of stars, so Brian can have a day off.

I don't know if any of you come to this show, have you been before, but his impression of me gets camper and camper.

Stranger and stranger is it?

It's not so much that, it's more as you've moved towards middle age.

I think all of us, we've got a little bit camper, haven't we?

With ourselves,

if you could teach American One Sentence, what would it be and why?

Just quark to confuse people as to whether it's a physicist parrot or just a posh duck.

Don't eat me, I'll only end up repeating on you.

Nice.

Strong and stable.

One here, I think, exercising excellent pop culture judgment.

Things can only get better, the best lyric ever written.

So, thank you very much to our wonderful panel, Tim, Katie, and Steve.

And we should, now we've got to the end, we should say, well, a couple of little notes.

We've had an edict from Radio 4.

As many listeners will know, BBC Radio 4 is actually powered by the number of complaints it receives.

If no one's outraged, disgusted, or miffed, then the generator starts to fail.

And now, see, in the old days, we were always receiving, well, we received a very large number of complaints.

The first section of complaints were about the fact that the infinite monkey cage may well be cruel to animals.

This is entirely true.

How seven monkeys haven't written a Mills and Boone, so how can an infinite number write Macbeth?

And we used to receive hexes from witches.

And this, unfortunately, all of this has dried up.

We used to get so many complaints, it created so much energy that we actually managed to power an automated walk-in bath for Nicholas Parsons.

So, before Radio 4 fizzles out due to accidental listener contentment, we've been instructed to make umbrage by taking over Radio 4 for a day and making it more evidence-based and compliant with the laws of nature.

So, the shipping forecast will now become the climate change forecast.

There will be stormy conditions for boats sailing into the port of Leicester.

That'll get Nigel Lawson annoyed enough to pair a couple more shows.

Does Island discs will be cancelled due to rising sea levels?

The archers will be genetically modified.

Wait until you hear the size of those cows.

And Richard Dawkins will be presenting Thought for the Day.

There's no such thing as fairies.

Hmm.

Anyway, so, and John Humphries will be forced to talk about a technological innovation without sounding like he's the kind of man who would smash a loom.

So there you go.

So if you're going to complain by email, please use caps lock and email to slash dev slash null at bbc.co.uk.

Yes, it's Brian's classic Unix joke.

Thank you very much, my light.

In the infinite monkey cage,

in the infinite monkey cage.

In the infinite monkey cage.

Till now, nice again.

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