CHRISTMAS LECTURES 1973: Sir David Attenborough - Be Mine

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How do animals go about attracting a mate? Sir David Attenborough reveals the secrets of courtship in the animal kingdom.

Breeding is a natural part of the animal kingdom. Animals need to seek out a mate, with males and females often cvoering long distances in search of the right mating signal.  

Across the animal kingdom, species have developed myriad ways to advertise for a mate. Males possess territory to attract their mates and females have devised ways to announce their presence to the searching male.

When together, animals have further problems to solve particularly when it comes to language. Males need to switch from a language of aggression to one that will encourage a female to stay with them. Oddly, the languages of threat and courtship are remarkably similar. On top of this, there are other more characteristic signals involved in courtship, such as indicating suitable nesting sites, or feeding the mate.

Every species of animal has developed its own special system. These distinctive messages act like passwords, preventing animals of different species trying to breed with one another. It is this language of courtship that has given rise to some of the most beautiful and extraordinary sights and sounds in all of nature. 


Natural World, Being Human


Sir David Attenborough
London, UK
Filmed in:
The Theatre

Royal Institution, BBC

Collections with this video:
CHRISTMAS LECTURES 1973: The Language of Animals

Licence: Courtesy of BBC





If you want to raise a family, one of the first things you've got to do, is to get a place to do it in. And that applies to us, and it applies to a great number of animals. And one of the ways in getting a place to raise your family in, one of the things you have to do then, is to get rid of other people who may want the same place. And animals have lots of ways of doing that.

Birds, of course, do it a great deal. Birds do it by singing, many birds, many songbirds. That's the function of birdsong, or one of the functions of birdsong. And ornithologists, people who study birds, learned quite a few years ago that if you want to take a photograph of a rare bird, or indeed a not so rare bird, you want to take a photograph of a robin. One of the really cunning things you can do, is to get a recording of a robin's song in springtime. And take it to a place where you know a robin is setting up his home. And play that recording. And the robin is outraged. He comes down and he sings to your recorder, answering the challenge of the recorder. Well this is a well-known trick.

And a few years ago I was in Madagascar, trying to find not a robin, but a rather rare kind of primitive relation of the monkeys called a lemur. And a particularly rare one, a giant lemur. And we were in the forests in eastern Madagascar. And we had no difficulty at all in hearing this noise. [LEMUR SOUND] I can't hear it on the speakers just yet. It will come through I expect. Can I hear it on the speakers? I can hear nothing in the loudspeakers and neither can you. [LEMUR SOUND] There now. Thank you very mu - Thank you very much indeed.

All right. So that was a very weird call when at last we got it. Which I knew came from this rare animal. But for day after day after day, we simply could not see it. So eventually I decided that what I would do, would be to do just that trick with the robin. So we went off into the forests with this particular recording. Turned the machine to replay. And played back this sound. [LEMUR SOUND]

To start with, no reaction at all. And I thought for some time that the trick wasn't going to work. And yet I was sure that this particular lemur, called indris lemur, was a territorial animal with - [LEMUR SOUND] And there was his reply. [LEMUR SOUND] There again. But again I couldn't see him for about, oh a good three or four minutes. [LEMUR SOUND] And then, there he was. He was about 25 yards away, halfway up a tree. And he seemed to be fascinated by this recording that I was playing to him. But you notice that he is not singing the call which I'm playing to him. He can't think where it's coming from, because I suspect that he had never imagined that another rather tinny indris could have invaded his territory.

There were two of them, one below the other. And both were equally fascinated by this sound that we were playing them. Well, they didn't stand it for very long. After we'd been playing this to them for a bit, they got really quite alarmed, and decided that they would move off. And they are, I think, some of the loveliest leapers in that tribe. They've got very long back legs, as you can see. And soon they were off. There they go.

Well now the point is, you see, they had two calls. And already you will have decided that they've got two expressions in the lemur language. The first was that wailing call that I played which says, this is my land, this is my territory. And isn't aimed at anybody in particular. And the second one was this hooting noise, which is anger, which is outrage, which says get out. Now of course noise, language, that sort of sound language, is one way that animals can say get out. But animals could also say, this land is mine, with visual signals.

This chap comes from Cuba. And he's a bit lively and if I'm not very careful, he may get out. So I'm going to go easy with him. There, thank you very much. Now this is an Anolis lizard and he comes from Cuba. And he is very territorial. Now see that - Do you see? Below his jaw there, just as I was talking, he stuck his membrane out. Come on. Show us again. You see? He's got a pink membrane. I wonder if you're - There. Ah. Now you see he's furious. Do you see? He's got this thick membrane here which comes out below his jaw, and which in some kinds of Anolis is even more brightly coloured than this. This one is a sort of pinky yellow. And he erects this just like a flag. So that he sits on a branch and flicks up this flag which says just the same thing. Now that's a relief. Says just the same thing which is, this is my land.

Fish, of course, do just the same thing. Fish have already got ready for them, they don't have to develop little flaps under their chin, because they have already for them the magnificence of their fins. And if you keep fish, tropical fish, you can see how they display their fins one to another. And they flex them and they often change colour. They go black. And they - you see they're showing it side by side. And then they grab one another's jaws.

Now the important thing is, that these particular fish could easily kill one another. And what's more, they do if you keep them in too small a tank. But in their ritual of territorial fighting, they don't. They have this display. And now they will let go. And once again, they will show their fins to one another. Which often means, I'm going round and round and round and round and showing off the splendor of their fins, which is a mutual display to one another to say, keep off, this is my land.

Now of course fish can easily do that if you're living in an aquarium. Because if you're high up or if you're high up in the water, fish below you and to the side of you, they can all see your fins. They can all get the message. They can all read your notice, which says keep out. They can all hear the message which you are giving. They can all see the message which you are giving, keep out. But of course, what happens if a fish goes out onto dry land? If a fish went onto dry land, it would have considerable problems because there would be nothing beneath it. And there would be nothing above it, and it would have difficulty in sending that message.

Well, there are actually fish that do climb out onto dry land. They're called mudskippers. If you go to the tropics and look in the mangrove swamp, crawling over the mud, you will see strange little fish like this. Mudskippers. And they each have a little pond on the bottom of which is their hole. And that's their territory. That's their home. That's the place that they defend with keep out notices. And how do they do it? Well this particular species does it like that, which is by showing the dorsal fin on his back. He erects it and it's brightly coloured. Now watch. There, you see? He flicks it up. And so does that one.

And there's another species which is even cleverer. There's another species which in addition to that fin on the back there, has got a tall mast so that his keep out notice can be seen from big distance, there. And there's yet another kind of behavior where he actually jumps into the air. So that fish way over the mangrove swamp can see him. There. The first time I saw this, I couldn't imagine what it was. Like a spout of water coming up from the crab. Extraordinary sight.

So those are methods whereby creatures of all kinds, before they start to say, be mine, to a mate. Say, beware and keep out, because this land I want for me. Now obviously, that serves very important purposes. Because if you're going to set up a family, one of the things that you need is a good supply of food. And if you're a bird, or indeed if you're a mudskipper, or if you're a lemur, that means that you want a supply of insects, or you want a supply of leaves, or you want a supply of algae, or you want a wide variety of food supplies. So therefore, it's very important that you shouldn't have too many creatures all clumped together. And so the purpose of these calls which say beware, is to spread out the species, to spread out the kind of animal widely over the land. So each has his own little patch of territory where he will be sure that he gets enough food for his babies.

OK, so now we've got our land. We've got our little establishment. What do we do now? Now we have to make sure that we're going to get a mate. That the female is going to come. And how does the female know? Well once again, there are many different languages that animals use to summon females. And one of them, let's start with - What should we start? We'll start with a bird which doesn't do it with song, but does it by signals.

In the tropics, on the small islands, the ocean islands, there are marvelous birds called frigatebirds. And the male, when he nests, develops this enormous balloon below his throat which he can blow up. And he sits in the top of the low, scrubby bushes where they make their nests. Having claimed his place, his place in the sun, as it were. And he signals to the females who fly above him by this call and this great big red throat sack, which says, I've got a great place. Come and join me. That's a female. And all the males do this in competition with one another. And one supposes that the bigger the balloon, the more effective the signal will be. And the female comes down. And when she does come down, they make a nice is little whirring noise together. So they have come together, male and female. And now they'll be in a position to mate and start a family.

But of course, the much more common way of birds attracting mates is this way. [BLACKBIRD SOUND] Now you all know what song that is. Do you know what song that is?

A blackbird.

A blackbird. Is that what would you said? Yes, quite right. That is indeed a blackbird. It's the sort of sound that we'll be hearing in another few months. Now this song, which is so familiar to us, and which many of us may think is so beautiful, actually has got lots of messages in it. What could we deduce from that song? What does that actually tell us? Can you think of some of the things it might tell us? Give me some suggestions.

Where the bird is.

Where the bird is. Very good indeed. In other words, the female will know that this particular bird is in that particular place. Correct. What more?

What kind of bird.

What kind of bird it is. Which is indeed the message which it tells us and which it told you. So that's two things it tells you. What else?

That it's got a nest built.

Indeed. In what sort of emotional condition it is. That it's ready, as it were, for nesting, correct? One more, can we?

How good a singer it is.

How good a singer it is. Yes, that's true. And actually it's perhaps even truer than you think it is. Because not only does it tell you what sort of singer it is, it actually tells you which individual bird it is. Because the fact of the matter is, that no matter what you read in those books about watching birds, where they tell you all these funny words as to how you actually recognise a birdsong, the fact of the matter is that every blackbird has a slightly different song. And that it is absolutely possible that female blackbirds, hen blackbirds, can recognise their own mates. Not only that, but blackbirds in this country have different accents. It is possible for a blackbird to sing with a Yorkshire accent. It is possible for blackbirds to sing with a Scot's accent.

And if you are clever enough, you can actually know from the recording of a blackbird - I should hasten to add that I'm not and I don't know - but some people know when they hear a blackbird call where that blackbird was recorded approximately. And they do so by analyzing it in the spectrograms, those diagrams which I showed you last time. So the blackbird song has got a number of messages in it. Where it is. Who it is. What condition it is in. What kind of bird it is. And what it is doing on top of those three things, four things, is to further messages. First of all, keep out to other male blackbirds. And secondly, come along here to a female blackbird.

Well now that was an easy thing for you to recognise. I wonder if you'll recognise this. [BLACKBIRD SOUND] That's still a blackbird. We will move on a bit. See if you can recognise this. [WHALE SOUND] What a well informed lot you are. Yes.

A whale.

A whale indeed. Let's listen to it for a bit. It's a humpbacked whale. [WHALE SOUND] Now the extraordinary thing about that is that that is a song, just like the blackbird's song is a song. We call a call a song when it repeats, when it is a regular pattern of notes, like a tune. When it's not just a random selection of notes. And when it's not just a short burst of noise. But a song with a regular pattern to it.

Now a blackbird's song may last a minute or so. But a whale's song may last up to half an hour. So it may sing a pattern of notes for a good 30 minutes. And only then will it repeat them. But when it does, it repeats them very accurately indeed. And it's partly because of that very long period that it was a long time before scientists actually recognised that what they were hearing was indeed a true song.

There's another remarkable thing about it. And that is that underwater you can hear much farther, and much longer distances than you can on land. Air is not a very good way of transmitting sound. Water is a good way of transmitting sound. And it may well be that's the whale's song can be heard up to 100 miles away by other whales.

Now the fact is that this has only been recognised as a song amongst the humpback whales since about 1967, when an American scientist, called Dr. Roger Payne, first studied them. And we don't know whether that is a mating song. Whether in fact, this huge 50 foot long animal is lying down in the depths of the ocean singing this song, maybe calling to a female 100 miles away. But it could well be that that is indeed what it's doing.

One of the tragedies, of course, is that we may never know what that song is. Because the humpback whale is becoming increasingly rare and is getting closer and closer to extinction. Because we human beings kill humpback whales in order to make margarine and soap, which you may well think is a crime and a scandal. However that maybe, one can only hope that the humpback whale will indeed survive and let us know more about the function of such extraordinary songs.

Well, of course, from a very, very big animal that has a mating song, if indeed it is a mating song, let's go to a much smaller creature, which also has a mating song. And this you will recognise. Grasshoppers. Grasshoppers, of course, make a song which we all recognise during the summer. And that too is a mating song. That too is summoning the female. And he makes it by scraping his thighs up against the edge of his wings. And he listens to it through an ear which is not on his head, but which is on his abdomen. But that song is in many ways serves the same purpose as a blackbird song, or indeed, a whale song. But you've seen grasshoppers before, and you're not surprised by that.

We've seen ways in which animals summon their mates by vision, like the frigatebird. By sound, like the grasshopper and the whale. And there's one other sense, one other way that we could exploit in order to summon the mate. What's left if you've used sound -


Smell, indeed. Smell. Well, there are some animals that send smell messages that have the language of perfume, if indeed you like to call it that. Moths particularly do that. This is the moon moth. Now the female moon moth has a perfume which can be detected by the male moon moth up to seven miles away. And there are some sorts of moths, the silkworm moth for example, which also communicates by perfume, has something like one and a half milligrams of that perfume material, substance in her. Which is enough to attract seven trillion moths like itself, which is probably more than exists in the whole world. So it's a very powerful and yet very sensitive method of communication.

Now, as I said, it is the female which emits the perfume. And it is the male which detects it. Let's see just what that means in terms of different structure. Let me take out this one and put it there. Now then, on the screen you may be able to see that it's got antennae just there. Now let's look at the other one, without saying which they are. And this one, I think, there has rather larger antennae. I wonder if I can get it better in the screen for you. There we are. Now, do you see? That has much larger antenna than that. And that is because moths smell by their antennae. And so this one is the male moth, which has the larger and more sensitive antennae in order to perceive the smell which is produced by that one.

But smell is used by all sorts of insects and many other kinds of moths. And the smell-producing substance, which causes this attraction and which ultimately leads to mating, is called a pheromone. Now who will come and smell this? You're very brave. You come and smell this one. It's a bit strong.


Bwah. Now that is actually ammonia.


Not very nice is it?


Not very strong. Someone else come and smell the next one. You come and smell this next one. Do you like that?


You do? What is it, do you think?

I don't know.

It's very nice. That's eau de cologne. You can easily smell it. It's quite nice and quite strong. Now who's going to come and see the third one? You'll come. And this is the pheromone. Now can you smell that?

Yeah. It's quite strong.

It is, isn't it?


But actually, let's test you. Do you think it's as strong as that?


Now the fact is, it's very curious that this pheromone is much more active, as far as the moth is concerned, than either those two things, you see. They don't attract it at all, but this does. Thank you very much.

Now the thing is, I've actually got some of the moths that this is supposed to attract. Now, I don't know whether it's going to work. There they are. These are warehouse moths. What may happen - and I don't know whether it will - what may happen is that if I put some of the substance in there, they may get very excited and they may indeed mate. And let's just see whether they do.

Well I - Yes, do you see? A lot of movement. Did you notice that there was absolutely no movement at all before I put that in? And now they are getting very excited, which is a great relief to me. And I think they are beginning to mate. I think we can count that experiment a success. [APPLAUSE]

So we have actually summoned our female. We have got our territory. We've summoned our female. And we have, in this instance, at any rate produced the right sort of stimulus, the right sort of message, which leads to mating.

But there is one little necessity which I've left out. It's no use mating unless you mate with the right kind, with your own kind, with your own species. And animals have lots of languages and messages to make sure that you mate with the right kind, that you attract the right kind.

Let's see this one. Now this is a toucan. Indeed it is. And it's a particular sort of toucan. It's Cuvier's toucan. Whether it knows it or not, that's what it is. And all toucans, of course, have a very large bill. And every one of those bills in each species has a different colour to it.

This one is - Now he may display it. Their song is a very harsh simple note. And that in itself is a clue. Because just as the blackbird has a very complicated song, which says I am a blackbird, so the toucan doesn't rely on its song to do that. But does it sends the message in a different way? It sends it on its bill. It, as it were, has a flag, which says, I am this particular species of toucan. And the other pieces of toucans all have different coloured bills.

So that one of the functions, at any rate, of these long beaks, which incidentally are very light. You might think the toucan, when it flies, gets sort of top-heavy, nose-heavy as it were, fall into the ground. But actually the beak is just spongy and empty and very light. One of the functions of that beak is to proclaim just which sort of toucan he is.

The other function - [TOUCAN SOUND] He's doing that little growling call. The other function, I think almost certainly, is a very delicate pair of forceps to pick off little berries from the ends of branches where he can't get. But the reason that they are also differently coloured is, I feel certain, because the bill colour serves as a label to say what sort he is, so that his mates will recognise him and he will recognise his mates.

Now you may say, why should a bird be so fussy, that it should only mate with another of its own species? Well a number of reasons. We think that each species of animal in the world is particularly adapted for one particular part of the web of life. It fits it nearly perfectly. If you have two kinds which get together, then the offspring will neither resemble totally one nor the other, or is at least unlikely to. And therefore, to that extent, will not fit that part of the environment. And similarly, we also know that often when you get hybrids between two species either there's difficulty in mating, in fertilization, or the hybrids, the product of such a union, are themselves infertile. So it is actually very important that animals should be able to know their own species. Thank you very much. I think we'll leave you. [APPLAUSE]

And just as he does it with a flag on his bill, so other animals do it with gesture. If you go back to those mangrove swamps where we saw the mudskippers, we'll see creatures like this. Fiddler crabs, they're called. And each of those has a different sort of gesture. Here's one. See there's a, what you might call a groper. And this tiny, little white one which does a quick jerk. Each of these, and here's - Watch this one. Oof. A bit of food. Oof, again. Each one of these is a signal to others of its kind saying, I am a particular sort of mangrove crab, or fiddler crab. And so that too is a method of making sure that you attract your mate of the correct species, of the same species.

Now is there anyone here who knows semaphore? Anybody? Do you know semaphore?

A little bit.

A little bit. Anyone who thinks they know more semaphore? Anyone in the back? Madam. Yes, anymore? Do you know semaphore? No. Do you know semaphore? You know semaphore. Right. Come down here. Now do you know enough semaphore, do you think, for you to be able to send a message to that lady up there? I hope she knows enough semaphore.

I don't think so.

You don't think you do.

Well, you see I've only been at scouts for a little time and I'm learning it. I'm learning it.



Have you got a very long name then? Is your name Algernon or anything like that?

No, David Williams.

David Williams. Do you think you could - Well now we've let the cat out of the bag now. Well if you've only just learned, let's see if we'll ask him. Will you come down? And don't you tell me what your name is. You see if you can use those flags, and without saying anything, say to that lady up there what your name is. If you know semaphore, you stand there and see whether you can see what he says. Very good. Did you get that? Did you get that?

Well I think the first letter was something like an R.

It was very, very little like R really. I'd like to help you and say, well but I think it was probably an A. Was it an A? It was. Do the next one. Yes, which is?


And the next one. A. And what's the last one?


Alan, Alan. Correct. Thank you very much indeed. Thank you. Now you see the point of David and Alan. Thank you very much. The point about this is that first of all, Alan if I may say so, did it very well, did it very jerkily. Like that, very distinct. And he used flags. Because he wanted these particular gestures to be very easily seen.

Now animals do just the same thing, some animals. Some animals, actually, they don't send the message, Alan or even David. But they do send messages which are comprehensible to other animals. And they do it in just the same way, by using their feelers, or their antennae, or their pelts which are then very brightly coloured in order to emphasise this point. Let me show you.

Spiders are great ones for this. This is a hunting spider, which has very good eyesight. And here the semaphore starts. You see? Now here's another species. He's got sort of boxing gloves on. And it's very interesting. When you look at an animal, any animal, it's very interesting to look at the way in which it's coloured and try and decide why it is coloured that way. Because every bit of colouration that you see on an animal has a reason behind it. Whether it's camouflage. Whether it's warning, as we saw in the first program. Or whether it's these sort of signals.

Look at this one. He's got a very special movement that goes with it. Bit of a tremble and a flash. You see? Raising himself on the ground. And that is a sort of semaphore. So saying that you are the same species is one thing, but you actually have to say what sex you are.

Now there's a good old story. Everyone says, how can you tell the difference between the gentleman seagull or a lady seagull? And people say, that only matters to another seagull. And everybody laughs. But it's not so funny, because there are some animals which are almost identical. And the animal's got to discover somehow which sex the new one it is meeting is.

Penguins, for example. Many penguins are identically coloured. There's one species of penguin that has a very simple method of discovering what the other penguin it happens to meet is. What it does is it brings a pebble. And it carries a pebble in its beak and it puts the pebble at the feet of another penguin in whom he might be interested. If the other penguin fetches him a smart blow behind the ear with its flipper and gives him a peck, he knows he's probably met another gentlemen penguin.

If when he puts the pebble down, it just turns away and ignores it, it's very likely that what he's met is a female penguin, who unfortunately is not interested. If he gets the pebble and puts it at the foot of another penguin and this other penguin give him a low deep bow like that, then he knows that he's met his mate.

So you see, animals actually have to discover what the sex of the other animal is. And this leads to all sorts of complicated behaviors, complicated messages. One of the loveliest of which comes from a big seabird called an albatross. And I will just let you see the greeting displays between a male and a female albatross who've already met. Here this one's coming home. And here's its mate. There, now watch. That's the beginning of this courtship display. A bill clatter. [ALBATROSS SOUND] Now this is not just - I beg your pardon. This is not just anyhow. This sequence, this order of gestures, this order of beak clattering, this order of braying that happens always in the same order. And always, or nearly always, when the two birds meet for the first time after a period apart. Very touching too.

Now what should be the function of that, once you already discovered that you are a pair, what does that sort of display do? Well what we think it does is that it cements the pair bonds, cements the union between the two, male and the female. It creates an emotional atmosphere, which means that the female in herself begins to produce eggs. And it leads to the moment when mating will take place. It does all those things.

And it's not surprising when you've seen a display like that to know that unusually for birds, that albatross mates for life. And once they have formed those patterns, those pairings, they will remain as a pair for the rest of their lives. Now it's a very bold statement to say for the rest of their lives, because if you really want to be scientifically sure that that is correct, you have to watch a bird for as long as it lives. And there was a study done in New Zealand on those similar albatrosses for 16 years. And we know that, as a result of that work, indeed there are albatrosses that do remain together for the bulk of their lives, which is very touching.

Now let me play you a different sort of mutual display. That is to say, a communication one between the other between pairs, which doesn't use gesture like the albatross, but uses sound. Listen to this song. Now this is an East African bird, a shrike called a boubou shrike. And you may think that's a pretty boring sort of song. But the interesting thing about it, is that this is not made by one bird, this is in fact made by two birds.

You notice that the song is always the same. It go bah bum bah bum, but there is that squawk in the middle of it. Now that squawk comes from the mate of the first bird. And I cannot say whether it comes from the male or the female, because the fact is, it might come from either. Because these birds are expert duetists.

Listen to this one. This is the song of one of them. Just straight like that. And the birds may be quite widely separated, hundreds of yards apart. And this is the call of the other one of the pair. And when you put them together, they don't go together just any old how, but as you'll hear it, it's always on the third note. It's actually only between the second and third. Always in the same place.

And that is actually a very simple boubou shrike call. They have many calls. Some of the very complicated tunes, in which one bird will sing just one or two bars, as it were, of the tune in the middle. And the other one will begin the song or end the song. Now we know actually too that they can each start the thing or they could each end it. And we know, what's more, that they can each sing the whole song themselves.

And there's a rather a rather touching story about another dueting bird, an Australian magpie. A pair of which lived in a cage in an aviary. And after a long period they had a very long duet, which they always sang together. And after a long time, the female died. And after the female had died, the male actually sang not just his sections of song, sang the complete song entirely by himself ever after.

Now the function of that song, is again, like the albatross, to cement the relationship between the two, between the pair. And also, particularly in the boubou shrike's case, to make sure that the territory which they occupy throughout the year, unlike the blackbird which only occupies into the spring, the territory which they occupy throughout the year, is patrolled. And the two of them share of the work singing this joint song around the corners, from the singing posts of their territories.

Well that picture of married bliss, as you might say, between albatrosses and boubou shrikes, is one aspect of, if you like, married life in the bird world. But there is a completely different one which doesn't match our own human ideas to what is good and proper. And that comes from a completely different kind of bird, which doesn't marry for life, which doesn't pair for life. And indeed actually doesn't really pair in any way that we would recognise. Let me show you one.

On the prairies of North America there are birds like this. This is the sage grouse. And this is a male sage grouse. And he has this extraordinary display with these big throat patches. And there's a female, two females. He develops these patches in springtime. And he has this strange way of using this throat pouch to produce the sound. And the big sort of fur around his neck is set off by these spiky tail feathers. And the males all come together on a particular ground and display it to one another. Display as much to one another, it seems when you watch them, as they might display to the females.

Now this is a very strange piece of behavior. Because if you develop as extreme colours, as vivid a language as those patterns on those grouse, you can see that it might lead to all sorts of problems. Because if you are raising young, if you have little chicks and you were tending them - the sage grouse was tending them, with these very big patterns, these easily seen patterns, you can see that it would be very dangerous. Indeed if you're sitting on the nest on the eggs and you look like that, that would be very dangerous. Because the sage grouse has no way of concealing those things once it's developed them.

And the fact of the matter is that the sage grouse doesn't tend its chicks. It doesn't incubate the eggs. That what the sage grouse does, is that it goes to the display grounds in the springtime and there the males all display to one another and the females come and watch them. And here I must be careful because we don't really know, but it seems likely that the females decide who is the champion. Who's the big boy. Who is the splendid one. And they decide that partly from its patterns and its shapes, and partly from the particular place that it occupies on the display ground, and then they will mate with that one bird.

So that the boss birds, the king birds, become the parent of a high proportion of the population, the breeding population that year. And many of the other smaller male birds don't get a look-in. They may do later on if they grow bigger, but at that stage, they don't. So that the meeting between the male and the female is very, very brief.

Let me show you another family of birds where that also happens. Yes. This is a bird-of-paradise. And one of the few living birds-of-paradise in this country. Now the bird-of-paradise family is extremely varied. And this is a bird called Wilson's bird-of-paradise. And you'll see that its got a bright, blue head. And its got a yellow cape. And its got curling wires, it's so called, which come out from its tail. And it's got a scarlet back and an emerald green bib, apron.

And you will expect that the particular form of display which it goes into will actually display every one all of those extraordinary characteristics. And indeed when it does go into display it, which it does on branches low in the trees in the jungles of New Guinea, it swells out its chest, so that it becomes a great, green, glowing globe. And then it tilts it's head down so that you can see the blue at the top of it's head. It spreads out its yellow cape. And then, even more miraculous, it takes those wires at the back and puts them over its head so that they quiver.

And this bird, each individual has a particular tree where it will display. And it is likely that the females, which are drab little brown birds, little thrush-like birds really, go from arena to arena, from display post to display post, selecting which they will mate with. But that, as I say, there are 40 different kinds of birds-of-paradise and that is very unusual kind.

The more usual kind are these. Now you will think that Mr. Coates has done something funny to these birds. And that they are hanging upside down because of some frightful accident that had happened outside. Not so. This is the blue bird-of-paradise. And this has the extraordinary display of when it goes into display of hanging upside down, as you can see here, with these two wires, which aren't really wires. They're feathers coming from the back, forming a marvelous pattern at the back there. And then the whole of his chest throbs and shimmers, the blue bird-of-paradse.

This is an astrapia bird of paradise which has a green bib, a marvelous iridescent green bib there. Which again it expands and blows out when it displays. This is the twelve-wired bird-of-paradise, which when it displays again, extends its chest like that. And these wires, which are modified feathers, become very tense and they form a regular pattern on the outside of it.

And then this bird-of-paradise, which is the so-called lesser bird-of-paradise, is perhaps the most well-known kind, where plumes sprout from beneath the wings. Now each of these is a splendid dandy, which actually shares no part of family life, as it were, does nothing to do with nest building, nothing to do with tending the young, and spends most its time during the breeding season displaying in the trees. And that display is one of the most exciting things, I think, that you can see in the whole of the bird world.

Birds-of-paradise are restricted to New Guinea. And I've been lucky enough to see them in their display trees many times. This is the lesser bird-of-paradise like that mounted one. And each bird, just before dawn, they assemble in a particular display tree. And then as the sun comes up, they start practicing their dance and singing. And then as the sun hits the top of the tree, they will go into the very top-most branches where each of them has its own particular display perch, which it keeps clear and which it will contest with other birds that might come along. And again, in these trees, which may contain 20 or 30 birds like this, so as the tree is suddenly becoming to blossom with marvelous yellow plumes, they will squawk, and cavort, and contest against one another.

And you may never see a female. Because the mating, when the female selects its mate, the mating may not even happen in the tree. Sometimes it does, sometimes it doesn't. And they do this over a long period of the year, which must be a very exhausting process. You know that some animals and that some birds in display - the bustard for example, which are commonly on display - may lose up to a third of its weight during its period that it's displaying.

This is another kind of bird-of-paradise. This is called Raggi's bird-of-paradise, which has red plumes. And that's an adult male with full-grown plumes. But it may take several years for the males to develop these plumes. This is a young male. He has no plumes. As a matter of fact, I don't know that it was a young male. It could equally rather be a female, because it's almost impossible to tell a difference until they grow the plumes.

But now I know it was a young male, because as you see, it was displaying. It hadn't yet got the plumes, but it was going through the display dance like this fully plumed one is doing. There he is. And just a little downy plumes beneath his wing there. That's all he has so far. But in years to come, he will grow those plumes and he may well inherit or acquire or in some way move to a particular part of the display tree where he will even become the boss bird, the king bird. And when he does do that, he will get most of the females. That is to say he will mate with most of the females.

And here this bird is indeed a female. And this is a male, a fully plumed male which is now courting her and displaying to her. And so you see that in the bird world, the gaudy ones, the ones with the most splendid plumage, the one with the most vivid messages are the ones which really don't have a family life, in the sense that many birds do. And it's a pretty good clue that if you see a bird with particularly splendid plumage, which is very different from the female, which has very drab plumage, like let us say a peacock, or a hummingbird or a pheasant, you can be pretty sure that those birds do not share in their family life. And that they leave all the nesting, and the incubation, and the rearing, to the females.

So those are some of the deductions which you can make simply from looking at the sort of visual messages that birds send one another. Next time, we'll talk about the messages that they send, not between father and mother as it were, but between parents and child. Thank you.

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