The Infinite Monkey Cage - The Secret Life of Birds

Episode Date: January 15, 2018

The Secret Life of BirdsBrian Cox and Robin Ince are joined by guests including Katy Brand, Steve Backshall and Professor Tim Birkhead to uncover the secret life of birds. They'll be looking at some of the extraordinary and cunning behaviour exhibited by many species of birds, both male and female, in an effort to attract a mate. They also get a special visit from Brann the Raven, who takes to the stage to demonstrate just how intelligent some species of birds can be. Producer: Alexandra Feachem.

In our new podcast, Nature Answers, rural stories from a changing planet, we are traveling with you to Uganda and Ghana to meet the people on the front lines of climate change. We will share stories of how they are thriving using lessons learned from nature. And good news, it is working. Learn more by listening to Nature Answers wherever you get your podcast. Hello, I'm Robert Eades. 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 and otters. And he doesn't like anything that can't be explained in a one-line equation. I'm just going to get complaints now. Are people going to write, why do you hate magpies and otters? I don't even know what a magpie and otter is.

I know they're made of muons and gluons, Why do you hate magpies and otters? I don't even know what a magpie and otter is. It's not... 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... LAUGHTER

Today, we'll be talking about bird behaviour. Genuinely, you are. 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 visualise the Earth's magnetic field.

Quantum. Mmm. Happy? Well, not really, because you're not a European Robin anymore, are you? You know? 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 birds. But we had to call it secret life because 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.

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's Steve Batchel. I'm a wildlife television presenter. And the thing that intrigues me about bird behaviour is the murmurations of starlings, the remarkable flocking behavior they undertake before roosting in the afternoon, the 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 behaviour 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's the best word. It is magnificent. So you're already through to round two. Oh, it's not how the rules work? OK. Now, that's him. 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 the 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 brachiosaurus to the

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

It's not correct to say that they are descended from dinosaurs. They are dinosaurs. Now in fact we're going to just move on quickly. We're slightly going to change the order what we're going to do because uh very often we have big egotistical guests on this show who get agitated if they're not uh introduced on time and this is one of those uh examples please welcome tonight's guest raven but quietly. This is... Also introduced Lloyd Buck, who, Lloyd, this is his wonderful Raven Bran, and we're going to...

That's the name of the Raven, by the way. It's not a Raven Bran, is what he said. It's a very strange way of saying it. Raven Bran is 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... He's a foot away from my head. But you said he's an average-sized raven, not particularly large. No, he's just your's an average-sized raven, not particularly large. No, he's just your average normal-sized raven that you'd see anywhere in the world, all over the northern hemisphere. 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? He's seven. Seven years. And you also said he might live... I was amazed by Raven's 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, I don't want him to cheat. He's a bit keen here. I'm wearing some quite large hoop earrings, which I'm just going to take off. Bran flew very close to Steve's head then. 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, 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 guess at the food. It's at the other end of the box,

so he's going to have to pull it through using this string. And in a matter of seconds, he's solved the problem and he's eating it, which is... The audience all want to clap, but we told them they can't. You're waving your hands in the air. Oh, that's a remarkable thing. But it is absolutely fascinating watching birds going through tests like this.

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 stage. He's now working out which member of the audience looks most delicious. He's had to be sent 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, thought i think tim would agree with this that ravens have the broadest problem solving abilities and of any of any bird i do believe in their in their ability to problem solve can you give give us an example of his behavior well it's like i would describe him as having a child with ADHD for life.

He never grows up. And so obviously he's very curious. He's very bonded with me. So we go out for a fly every day. He's like a flying dog, really. But the trouble with that is, you see, he's much cleverer than I am, so he's 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 offline and 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 he'll know I'll stop him. But then maybe my phone 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, boom. So that's one of his classic little ways of raiding me. Another thing is when we clean him out in his aviary 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 and put 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 cage, so I put 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 Brad in his travel case, I've got to let him out, oh, sorry, Brad.

So now what he does often, he'll sit in there with the door shut, even when I've let him go, and then he knows that he can trick me because sometimes I think, oh, I didn't let Brad out. When I go in with the food to say sorry, he bursts out and has to 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 in here again. Do you find by trial and error

that there are different forms of lock which will eventually be worked out in terms of these kind of moments of great escape? Well, I'll just... Oh, yeah, you don't have water. He had a very good look at Robin then. Cheers. Can I get away with that?

They're all as different in characters, I would say, the birds, as you or I, and especially with the corvids. 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 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 get 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, the crow family, that are best known for having really intelligent kind of appearance to them. But we've done tests with with kears alpine parrots in new zealand and also with a bird called the striated caracara in the falklands and we took in these these tests which they'd never seen before which were 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 be presented at the bottom and the first time that you place it out first of all these birds are following you around everywhere they're're a 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 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 i feel like i should cover up the fact it's been written in case we have a s-t-o-n-e an s-t-o-n-e And we're going to put it somewhere around... We're not going to 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. Which seems to be very close to the K-A-T-Y. The S-T-O-N-E is 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.

Yes! 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. OK, are we ready? Yeah. Come on, Bran. He's a good boy. Right then. I hope he'll take me for dinner after this. Just okay. We ready. Yeah, come on. There's a good boy right then He will he will take you for dinner yes

So this will be a demonstration of how well he understands language and remembers what's right where's your stone where's your stone? 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 in the way that before, when you've heard about certain creatures like counting horses and stuff, where there were various different...

Oh, that's everything blown off. That's all right. But this is so much nicer than a goose. This is nice. He actually whispered... So beautiful. While he was down there, he whispered to me, your shoes are very last season.

Hang on, I just... All he said to me was, never more, never more. I thought, oh... 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.

There's something about the movement and the beauty. Yeah. There we are. So he knows I'm getting... 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 then I suddenly realised he would look for it. And we'd done an experiment where we put that on a whole pile of... Oh, hold on. Brad... Oh, sorry, you've got a bag. You think there's something in there for him to eat. Brad...

He likes handbags. He likes going in handbags. Brad, I'm sorry, you've got a bag. You think there's something in there for him to eat. Brad. He likes handbags. He likes going in handbags. He knows people often keep snacks, you see, in their bags. So he thinks, oh, I'll go and look in there. Our audience are the kind that often go out and buy offal shortly before a show. This could go very wrong. He's lovely. He's a very sweet-natured raven. He's lovely.

He's a very sweet-natured raven. He's really sweet-natured and friendly. And they're like a lifelong companion, really. He's a huge time commitment. But he's worth it. So when you flew down there, obviously you want to make sure you know where he is. But if he could get out of the building,

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? He would find you and stick with you or stay where he is until you found him? Yes. We're a bonded pair. He knows, obviously, I feed him as well, but there's much more to ravens than just the food. But yeah, I mean, he's lovely. We go out for a fly in 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 it's 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... Yeah. Is that true? Sort of. I mean, people really don't understand play at all.

People say that. And corvids 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 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 Bryn. That was absolutely fascinating. It was brilliant. 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 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. So they also have a very big brain. But their intelligence manifests itself in another way. Like ravens, corvids, 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 is 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 there no one's keen i mean is there is the one bird where just when you think oh we're really finding out all these oh no that is a disappointment pigeons pigeons are nothing like as dumb as they're made out to be.

Exactly. The guillemot that I've studied for 45 years used to be called the foolish guillemot. 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 incredible 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 the 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... I just... 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 cockerel would wander around, we'd put her out again, and he'd come and mate and we'd collect the sperm and 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'd go, oh, it's you, love. I'm not going to bother.

If we gave him a new one, he goes, whoa. And we did it time and time again. They are super smart. Wow. Playboy 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 the fact that the 2003 Ig Nobel 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? Absolutely. 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. Lay it on me!

In lots of duck species... You're going to beat this. 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, 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 little pouches 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 extra-bear mating, basically rape. And...

Oh, my God! 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 poor old 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 by picking up roadkill birds in the spring are killed in huge numbers on the road and you can dissect them and so we dissected this female some 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, 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 spiralled. 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 tightens, 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 of a bird mating? Do you know what? I'd actually rather you didn't, because I'd like something, otherwise half this show is just going to be half 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 cloacal 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... You say deviant, but he's just enjoying life.

Let's not judge them. That's fair enough. 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 every single day. I noticed that laugh there come from people. People just remember some of the trousers you wore in Strictly Come Dancing, seeing 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 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 parent 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 Steve has said, most copulating birds, it 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 just sit side by side he's presumably whispering sweet nothing's in her ear and she's eating jaffa cake have i given too much away i opened the book a bit too wide there, I think.

And we thought, OK, this is fantastic. My guess is that this must be something to do with sperm competition. Nobody knew anything about varza parrots in the wild. We went to Madagascar, did a study, and sure enough, it is the most remarkable avian mating system. For 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 queue to copulate with 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 do they all bring food? Yeah, and they all bring... Because they're not sure which... Yeah, exactly. That's precisely it. And they all want to protect their young.

So is most of what we see, Steve, in terms of what we interpret as beauty within birds, 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 bowerbirds in New Guinea and Australia, which are 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 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 latticework igloo, with an array of different beautiful objects laid out in front of it it which the bird has selected to make it more beautiful i've even been to 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 the bulbs and the beautiful beetle casings were a whole bunch of

you know little plastic soldiers there's one called the satin bower beetle casings were a whole bunch of little plastic soldiers. There's one called the satin bowerbird, 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 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 of this as i was thinking of uh you know the peacock obviously is one 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 was in one of his books or 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 the burden, the evolutionary cost of having this enormous tail 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 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, OK?

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 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 on that.

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 metre long and obviously is, you know, 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 females. 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 signalling, which is down to the idea that if a male can demonstrate its fitness in a way that cannot be faked, that cannot 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 widow bird 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 in others. How complex is the social mating behaviour, the family behaviour?

OK, 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% 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 mute swan is one.

Penguins aren't, I'm afraid. What about puffins? We don't really know about puffins, but probably not... Everybody thinks puffins are cute. They're boring, come on. Wow, that's me told. Yeah, they're probably not absolutely faithful, probably a bit like guillemots.

So in guillemots, 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.

And that promiscuous behaviour 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 insight here. 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. OK, so that's been one of the explanations for why females seek extra-pair 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 extra-pair male are fitter in some way. Do they live longer? Do they have higher reproductive success? And they don't seem to, which is really disappointing because that was our best explanation for why females engaged in these extra pair matings. But if you've got two males and you've got a child, then neither male is sure whether the child is...

Are you going to get double the support? In most birds, after the expirating mating... Oh, we're talking about birds. Sorry, I was... 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 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. 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 bird world. They aren't in the mammal world. You know, as Tim said there, 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 mammal offspring are born quite capable, or they become quite capable quite soon? Because some theories with humans, isn't it, is that because babies are born quite capable, or they become quite capable quite soon? Because 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. 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 some form of ritual which keeps the pair together yeah that that's that's probably true and that that period is is extended depending on you know what skills that chick is going to need to live its life so 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 a lot of birds, in monogamous birds, it takes two parents, particularly in the case of an albatross, it two parents to rear one chick can we we've heard um the this remarkable descriptions of the the variety of behavior we've seen some of the behavior with the raven remarkable behavior to

go back to your initial statement about birds 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 characterise 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 behaviour, he said, 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 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 they're difficult things to measure and to quantify in a scientifically rigorous way. I know that sounds very boring, but that's the fact. About ten years ago, I was chatting to Bill Oddie about this, and he was talking about the fact that blackbirds have a variety of different 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... LAUGHTER ..I'd definitely be interested. To be fair, I think he was mainly interested in your Jaffa cakes. LAUGHTER This is...

Well, well done, Sik, for making... This is a proper biology show, cos 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, if you've been before, but his impression of me gets camper and camper. Stranger and stranger is a year's goodbye. 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 our sides?

If you could teach a parrot 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 judgement.

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, you see, in the old days, we were always received... 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 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 power a couple more shows. Desert 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... Yes, it's Brian's classic Unix joke. Thank you very much. Bye-bye. Bye. in the infinite monkey cage in the infinite monkey cage without your trousers in the infinite monkey cage

turned out nice again in our new podcast nature answers rural stories from a changing planet, we are traveling with you to Uganda and Ghana to meet the people on the front lines of climate change. We will share stories of how they are thriving using lessons learned from nature. And good news, it is working. Learn more by listening to Nature Answers wherever you get your podcasts.