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Of the 10,000 or so species of birds that roam our earth, there is no family as stunningly beautiful, yet staggeringly ridiculous as the Birds-of-Paradise. The family Paradisaeidae contains 42 species in 15 genera.¹ These birds live in the cloud forests of New Guinea, its satellite islands and parts of mainland Australia.

They are famed for their unusual plumage and striking sexual dimorphism.² Although it’s quite common for male birds to be more colourful or ornamented than females (think of a Peacock’s tail), the Birds-of-Paradise take it to a whole new level. They have ostentatious tails, iridescent feathers, features so unique they have their own names, like head-wires, capes or epaulettes.

They engage in bizarre courtship displays, dancing on the forest floor or morphing into unnatural shapes. Some have even developed unique ways to make sounds, either as audible calls or as feather rustles. One can even make its feathers sound like a machine gun.

This stunning diversity has captivated people for hundreds of years. Yet, it’s only in recent decades that we’ve come to understand why these birds appear and behave as they do.

History

With such diversity within a single family, it’s hard to know where to begin. But maybe the best place to start is with their name: Birds-of-Paradise. How did that come about?

The story goes back to 1519 and Ferdinand Magellan‘s attempt to sail around the world. He set out with five ships. Three sank, one abandoned the mission, Magellan himself died on route, but in 1522 one ship returned to Spain and in its haul it carried the most remarkable skins. They were the dried remains of the Greater Bird-of-Paradise (Pardisaea apoda). But they were odd: their feet and wings had been removed. The indigenous tribes of New Guinea prepared the skins in this way to better display the bird’s stunning plumes: a fountain of golden feathers that sprung forth from the bird’s flank.

These skins were traded widely among tribes and between neighbouring islands. When European explorers first encountered the skins they asked why this strange bird had no feet or wings. The locals on the Maluku Islands had never seen a living one, though. The skins had been traded from land further to the East. To satisfy the explorers they spun a wild tale. They said the birds lived in paradise, that they floated high in the heavens, feeding on cloud dew, and as angelic creatures they had no need for wings or feet. Humans could only glimpse them when they died and fell to earth. The legend stuck, and still today we know them as the Birds-of-Paradise. There is still a hint to this origin in the scientific name carried by the Greater Bird-of-Paradise: Paradisaea apoda: Bird-of-Paradise without feet.

As knowledge of these birds spread among European ornithologists, it sparked a mania in the nineteenth century. Everyone was champing at the bit to discover new species. There was a catch though: New Guinea is a long way away and the mountainous cloud forests where the birds lived were virtually inaccessible. Any expedition was going to cost a pretty penny. To bankroll these missions, ornithologists turned to royal patrons, promising that in exchange for finance they would name any new discoveries after them. Ornithologists are nothing if not honest folk. They were true to their word, and today many Birds-of-Paradise still bear those royal names.³ We have Princess Stephanie’s Astrapia,⁴ Queen Carola’s Parotia,⁵ the King-of-Saxony Bird-of-Paradise,⁶ Queen Victoria’s Riflebird,⁷ Count Raggiana’s Bird-of-Paradise⁸ and Rudolf’s Bird-of-Paradise⁹ (although today it is more commonly known as the Blue Bird-of-Paradise).¹⁰

But let me be clear: these ornithologists didn’t actually go to New Guinea themselves. Do you have any idea how onerous and tedious that journey would be? No, no. They merely funded other people to go and send back the specimens. Now, this is all good and well, but there’s only so much you can learn from looking at a dead bird. Especially if the bird is unlike any other living creature. For example, the Black Sicklebill (Epimachus fastosus) possessed strange ornamental feathers that fanned from its back. There was no other bird they could look at to get an idea for how it may have held these feathers in life, or what they may have used them for. The naturalist, Richard Sharpe, took a stab and came up with this:

It’s possibly my favourite image from the history of natural science. Not only is it an unquestionably beautiful artwork, but it is also completely wrong. The Black Sicklebill doesn’t hold its feathers like that at all. Instead, it cups them over its head, turns itself side on and takes on the appearance of something more akin to a black comet than any bird.

This is part of its courtship display and when the female comes in for a closer look, he will straighten up and loom over her like a black phantom or dancing cobra, with a line of iridescent feathers running down the length of its hood.

The Sicklebill is one of the morphing birds, and we’ll have more to say about them in a moment. The point I want to make here is that no ornithologist had even seen a living one display until the end of the twentieth century, so shrouded in mystery were these wondrous birds for so long.

For another example of how these birds mystified those who first examined them, we can look to the Twelve-wired Bird-of-Paradise (Seleucidis melanoleucus).

Just like the Sicklebill, when this bird arrived in Europe, no-one knew what to make of it. It had a velvet black head, with a lemon-yellow back. But extending from its tail were twelve wire-like filaments that bent backwards. This was most odd. Originally, it was argued they shouldn’t even look that way, that the tail had been damaged when the specimen was packaged for transport. In fact, this is exactly how the feathers appear on the living bird.

It was not until the 1990s, when David Attenborough filmed one for the first time, that it was finally understood what the feathers were for. Once again, it plays a role in the male’s courtship display. The male positions himself on top of a bare tree trunk, protruding above the canopy. The female will join him on the trunk and the pair will chase each other up and down, with the male brushing his tail-wires against the female’s face. Apparently the female Twelve-wired Bird-of-Paradise prefers to be wooed via tactile sensation.

Curiously enough, the black wires that extend from its rear aren’t even tail feathers. Rather, they are elongated central shafts extending from the yellow flank-plumes.

So, we’re only two birds in and already things are getting crazy. Let’s take a step back. Maybe we should begin with where they sit in the broader family tree of birds. It may come as a surprise, but these most extravagant fowl belong to the Corvid Superfamily. That’s right, some of their closest relatives are Crows and Ravens. Looking at any random sample of the males you would wonder how this is possible. But then you would be ignoring half of the birds. Take a gander at the females, and you see that not only is the underlying appearance of these birds rather drab and dull, but you would also understand how such a seemingly hodgepodge collection of birds are in fact all related.

The females are all remarkably similar looking. Take away the males’ showy costumes and you see the true similarities lurking just below the surface.

At this point it also bears considering one Bird-of-Paradise that is almost always overlooked: the Paradise-crow (Lycocorax pyrrhopterus).¹¹ Here you see a bird almost indistinguishable from a Crow, revealing the common linage these birds and the corvids share.

But it begs the question: why did this Bird-of-Paradise stay black and crow-like while all the others became as flamboyant as hell? We will answer that question, but first we have to understand something else: courtship. Because at its heart this is why the males look as gaudy as they do. For decades, ornithologists speculated about what function the feathers served.¹² As you may know, in nature nothing evolves that doesn’t give the animal some sort of survival advantage. But in the case of the Birds-of-Paradise all of this goes out the window. Plumes of such outrageous colour, length and structure should surely be a hindrance to survival. Charles Darwin once said, ‘when I look at a peacock’s tail, I feel sick’.

He said this because the peacock flew in the face of the theory of natural selection, because nothing that serves no benefit to survival should ever arise. To solve this paradox, Darwin came up with the idea of sexual selection: a process whereby traits are selected which the opposite sex finds attractive, and so the individual’s chance of reproducing is increased. If natural selection is survival of the fittest, sexual selection is survival of the sexiest. And indeed, for the Birds-of-Paradise, this is exactly what their feathers do. The plumes have been selected to do nothing but appeal to a potential mate.

How they use their plumes, though, is where things get interesting. In their quest for sexy domination they have developed a range of tactics, which can be broadly broken down into two categories. The first are birds that rely on their plumes as things of beauty. The second are birds that use their plumes to transform their appearance. We have already seen the Black Sicklebill do this. We’ll look at each strategy in turn, using examples from across the species, because, let’s face it, that’s really why you’re here: to see birds being weird. And the Birds-of-Paradise deliver in spades.

Mating Displays

Let’s go back to the bird that started us off: the Greater Bird-of-Paradise. There are several species that belong to its genus¹³ and they all perform courtship in a similar way. The males gather high in the canopy of a single tree. This gathering is properly called a lek.

To begin their courtship display they open their wings and throw back their golden plumes creating a cascading fan. When a female arrives to inspect them, the male will go through a series of choreographed moves. As we will see, time and again, these dances are always performed in the same way, with the same steps in the same order, because apparently it’s vitally important to get the choreography right.

First, the male will gallop up and down its chosen display branch, calling as it does so. It will then turn its back on the female, presenting the underside of its golden plumes for inspection. If the female likes what she sees, the male will progress to the next step and begin backing into her, flapping his wings as he does so. Next, the male will turn and begin buffeting her with his wings, tapping her head with his beak, all while making a beeping noise. This step can appear aggressive, but the females must be into it, because if this goes well, mating will occur.

People who have observed these rituals noted that every female will end up mating with the same male, ignoring all the others. This is true of all Birds-of-Paradise that display in a lek.¹⁴ David Attenborough speculated that perhaps the position the male occupied within the lek had more to do with how successful they are than anything else. That by dominating the top spot, it signals to the females that he is the fittest partner. If that is the case, the fabulous plumes and mating displays could be for the benefit of the other males, as a way of asserting dominance. The other more accepted theory is that the rituals are about impressing the females. Between the different species, female preference as to what constitutes sexy is largely arbitrary and so courtship displays have developed in all sorts of crazy directions. The closely related Blue Bird-of-Paradise (Paradisornis rudolphi) has a completely different strategy for impressing the ladies.

The Blue Bird is well named. It has a velvet back head with striking cyan wings, as well as the modified tail-streamers its cousins have. Unlike its cousins, though, the Blue Bird prefers to display alone. It also prefers to display from an upside-down position.¹⁵ It will hang from a branch and spread out its feathery tail, whereupon it will begin to vibrate and emit an odd electric-like noise.

The King-of-Saxony Bird-of-Paradise (Pteridophora alberti) has a similar solo display, although one performed from the vertical position. It will start a vine bouncing and then begin to swing two, long head-wire feathers around.

These extremely modified feathers extend from just above its eyes and can be up to twice as long as the bird. Usually the male keeps them swept back over its wings, but during display it will wave them about in an erratic manner, again while emitting an unsettling electric-like noise. The remarkable dexterity it shows in controlling these feathers is all the more astounding when you consider it does it all with the same muscles we use to raise our eyebrows. The feathers themselves are so modified, with the filaments completely fused together into tabs, that they don’t even look like feathers. Rather, they look and feel almost like plastic.

By now you will be coming to realise that the feathers we find in this family are without comparison in the natural world. We’ve already seen cascading plumes, wires and plastic tabs. These are extreme modifications, and whether it’s the tail, the head, the wings or some additional collection of feathers that simply don’t exist in other birds, nearly every member of this family has feathers which have changed in some way. The Splendid Astrapia (Astrapia splendidissima) is adorned with more iridescent feathers than nearly any other living bird.¹⁶ Some people have even called it the disco ball of the rain forest.

This kind of iridescent colouration, which is common to the Birds-of-Paradise, is created not through pigmentation, but the structure of the feather on the microscopic level. Down on the nano-level the structure of the feather literally interacts with the wavelength of light, scatting, absorbing and reflecting light that hits the feather at certain wavelengths and at certain angles. Because of the interplay between light and angle it means the appearance of the feather can alter depending on where you view it from. At one moment it may be green or blue, at another yellow and yet another completely black. It’s a trick of physics and the Birds-of-Paradise exploit it to full effect, often to accentuate their courtship displays.

When it comes to courtship displays, the more complex it is, the greater discretion the females show, looking for the tiniest variations in the dances that signify a male’s fitness. For many Birds-of-Paradise it takes several years for the males to reach sexual maturity. In their early years, they have the same bland colouring as the females, and will spend a great deal of time practising the moves they’ll need and visiting the display sites of mature males to watch the masters in action. It’s quite a humorous sight to see the immature and ungainly males practising their dances dressed in the wrong feathers.

Some of the most intricate rituals belong to those birds that display on the ground. To really highlight their moves and make sure there are no distractions, the males will clear a section of the forest floor of all leaf-litter. This clearing serves as their court, and some males will maintain their court site for years. Several species do this, including Wilson’s Bird-of-Paradise, the Magnificent Bird-of-Paradise (Cincnurrus magnificus), as well as the numerous Parotias. Of all the birds, though, the Parotias have the most elaborate dance routine.

In mentioning the Parotias, we now come to the birds that display by transforming their appearance. Unlike the other birds we have looked at, the morphing birds are less colourful. They tend to be jet-black, with just highlights of iridescent colour strategically placed to accentuate certain features. Parotias are a typical example. They are sometimes known as the Six-plumed Birds-of-Paradise, so-called because extending from above each eye, just as with the King-of-Saxony, they have three long quills, tipped with a black plume. All Parotias share specialised decompressed feathers that can be flared our around their body to take on the appearance of a skirt. They also have a patch of iridescent throat feathers. Each piece of ornamentation contributes to their courtship display. Of all the Parotias, Carola’s (Parotia carolae) has the most elaborate routine.

The display in complex and involves many steps. The male will move between the viewing branch above the court down to the ground. He will bow, bounce, flutter and sway. Each step increases in complexity and builds towards the climax: the ballerina dance. This dance has several elements, but basically involves flaring out his feathers to form a skirt or tutu-like structure around his body. He waggles his head quills in front of him before finally taking a dramatic pause. He dips his head and then flashes his iridescent throat feathers at the females watching from above. Repeat.

If the male is to have any chance of impressing the females, he will have to get each step perfect. Now, when he goes into the ballerina dance, this is where he transforms his shape. But we have to consider the transformation from the female’s perspective, watching from above. When he flares out his skirt he stops looking like a bird, and more resembles a black oval. His head-wires and patch of iridescent head feathers help to trace out the edge of the oval while he dances, and when he pauses to flash his throat feathers it makes for a brilliant contrast against his jet-black body.

Several other Birds-of-Paradise create similar effects.¹⁷ We have already seen the Black Sicklebill, whose extreme transformation skills stumped ornithologists for years. But there are others. The two most prominent are the Superb Bird-of-Paradise (Lophorina superba) and the Magnificent Riflebird (Lophorina magnifica).

Unlike the Parotias, these birds perform their courtship displays on specially selected branches or fallen logs. The Superb Bird-of-Paradise is capable of one of the most astounding transformations, changing from a small black bird into what is sometimes described as a psychedelic smiley face.

It pulls this feat off thanks to three key features, which when at rest don’t look like much, but when brought together become something quite stunning. First, and most obviously, the bird has a blue, iridescent, delta-shaped breast shield. Second, they have a velvet black cape that extends from the nape of their neck. And third, they have a matching patch of blue iridescent feathers on the crown of their head.

When a female visits the male’s display site, he brings these three elements together in an unexpected way. He begins by pushing forward the breast shield so it extends out to form the mouth of the smiley face. The next step is to take the cape feathers and roll them up over his head, such that they frame the shield, creating a kind of oval shape. He then lifts his bill, so that from the female’s perspective it bisects his crown feathers, creating the appearance of two distinct blue spots, which when paired with the lower shield and framed cape, give the impression of eyes and mouth on a black face. It’s an astounding sight.

Of course, this is just the beginning of the display. Once the female comes down to inspect the male, he will bounce vigorously around her, being careful to always keep her directly in front of him so as to maintain the visual illusion. As he bounces, he also emits a loud clicking noise. The most remarkable thing, though, is this noise is not vocal, but is rather produced by rubbing his wings together.¹⁸

Now, the Riflebird uses similar methods, but to create a totally different effect. Just like the Superb Bird, the Riflebird is also jet black with an iridescent patch of feathers right over his throat. Unlike the Superb and Sicklebill birds though, the Riflebird uses its wings to change its shape. When a female approaches it lifts both wings over its head. However, its wing feathers are highly modified, with the ends rounded off, which when lifted together create two geometrically pleasing semi-circles that frame its head. This is a modification that has selected for shape and appearance over the optimal design for flight.

The courtship dance involves the males jumping up and down on the branch, moving forward at first and then back. As he jumps, he swings his head from side to side, hiding his face behind his wings leaving only his sparkling throat feathers exposed. Just like the Superb Bird, he also uses a non-vocal sound as part of the ritual. As he lifts and drops his wings, they make a distinct whooshing noise, which, thanks to the shape of its feathers, is amplified in the direction of the female.

Birds-of-Paradise also make use of vocal sounds in their courtship. Although in the case of the Riflebird, this is more of a prelude to the display. The bird possesses a pure, loud, melodious call, capable of travelling great distances. He uses this call to advertise his location to any nearby females. It is also a message to any rival males that this is his territory.

Many Birds-of-Paradise make a range of unique sounds for similar reasons: the Blue Bird and the King-of-Saxony make static, almost electric-like noises, and a Sicklebill’s call sounds like a zap gun. But there is one Bird-of-Paradise that takes vocalisation to the next level.

Maybe ironically, the Bird-of-Paradise with the most startling voice belongs to the otherwise plain, crow-like bird, the Curl-crested Manucode (Manucodia comrii).

It creates a kind of juttering noise, that starts high and goes to a lower pitch. It’s rather an unnatural sound that has been likened to a UFO landing. It kind of has to be heard to be believed.

Now, these birds are different to many of the other species we have met. Almost all Birds-of-Paradise are polygamous, with males mating with as many females as they can. Not so with the Manucode. These birds partner up and they use their strange, haunting call as a way to keep in touch while they forage. It also acts to ward other couples away from their territory.

They can make this extraordinary sound thanks to a highly modified trachea.¹⁹ In most animals the trachea is only as long as it needs to be to connect all the anatomy up. In the Manucode, though, the trachea extends in between the skin and the muscles all the way down the length of the torso, before looping and coiling (sometimes twice) and heading back up to the the lungs.

When they make their call, they really throw their whole body into it. You can see their throat inflate as their trachea fills with air, their wings flutter, they tip their head back and lunge forward as they go through the length of their call. Even though the Manucode forms mated pairs, the unusual vocalisation must still play a role in sexual selection, because, once again, only the males possess the specialised trachea. It goes to show, it isn’t just the outrageous plumes that make the Birds-of-Paradise unique, because even this plain looking one has attributes no other bird has ever evolved.

Speaking of evolution:

Evolution

It’s time to come back to the question that kicked us off: why have the Birds-of-Paradise evolved in this way? If we look at the plainer birds, like the Manucode and the Paradise-crow we find our first hint. It’s no accident that the birds who form pair bonds aren’t as fabulous as those who don’t. The primary purpose of the feathers is to entice a female to mate. Once this happens, the female goes off on her own. She makes the nest alone, incubates the egg alone and raises the chick alone. Meanwhile, the male’s only mission is to mate with as many females as possible.

A male who works as part of a pair to raise its young has no need for showy feathers. He’s value as a mate comes from the assistance he gives to rear the chicks. If a male isn’t providing a service, then mate selection must be done on another metric. Ultimately, appearance will always be the deciding factor, as appearance is the best measure of a male’s health and strength.

The same is true with all birds. As a general rule of thumb, the greater the difference between the sexes, the lower the chance the male will play any role in rearing young. This is true of ducks, game birds, hummingbirds and pretty much any bird with a complex mating ritual.

As mentioned above, the reason males look so marvellous has nothing to do with their feathers providing any survival advantage, but rather comes about as a process of sexual selection, driven entirely by the females. For it is the females who decide which male they will mate with, based on how desirable they find their traits. Quite literally, the females have forced the males into these bizarre behaviours. It’s almost as if the males have been evolutionarily trapped. Over many thousands of generations of mates being selected for the splendour of their plumes, these traits became exaggerated to the point where the feathers are a hindrance. Take, for example, the Ribbon-tailed Astrapia (Astrapia mayeri).

The bird possesses the longest tail in relation to body size of any bird. It has two white plumes, which can grow to over a metre in length. On a bird that is only about 30cm in size, this is quite a sight. And this long tail is nothing but cumbersome. Watching it in flight, the tail trails behind it like a banner being pulled by a small plane, providing nothing except drag and sapping the bird of energy.

This trait arose, not because it had any use, but because female Astrapias, for one reason or another, happen to prefer males with long white tails. And so it goes with every Bird-of-Paradise.

This form of evolution is called sexual selection and it differs from natural selection. In natural selection a trait will be passed on down the generations if it is useful to the animal’s survival. In sexual selection a trait is passed on only if it assists in getting a mate. This is the reason why the females have remained plain: under this system they have no need for extravagant plumes, and so they did not evolve.

It is also worth mentioning that under this system the male is motivated to mate with as many females as possible. As careful and deliberate as the females are with their choice, the males are just the opposite, and any female will do. This is to be expected. The female has a lot more skin in the game, considering the investment she must make to raise the chick alone. This makes the males a little overly willing to mate with anything that looks like a receptive female.²⁰ It is then curious to note that so many of the mating displays place the male in an awkward situation. Take the Greater Bird-of-Paradise who displays by turning his back on the female, or the Parotias which display on the ground while the females watch from above, the Blue Bird that is literally upside down, or even the Riflebird that displays by waving its wings in front of its face. In each instance, the female has selected for a ritual that places the male on the backfoot.

It’s a method whereby the female can watch the display and take time to deliberate before selecting a mate, while the male, if he becomes over-eager and attempts to forcibly mate, will find himself in a compromised position, allowing the female time to take flight and avoid an unwilling coupling. The females have effectively selected for rituals that keep the males at arm’s (wing’s?) length until she is willing to take things to the final step. In every meaningful way, the females are calling the shots.

But still, we are left with the question of why. Why is this the only family of birds where runaway sexual selection has occurred to such an extent? To answer that we need only look to their home of New Guinea. On this island these birds have no natural predators. Bright conspicuous plumes that might otherwise betray a bird’s location to a stalking carnivore are not an issue, and so the males can get away with being as showy as possible.

Second, in their forest home, all year round, they are surrounded by energy-rich fruiting trees. A female raises her chick alone, because she can. There is so much food available that getting enough for her child is something she can do without assistance, which usually isn’t the case with other birds.²¹ Likewise, for the male, because finding food is so easy, they have surplus energy that can be put towards growing outrageous feathers. They can also dedicate an inordinate amount of time to learning and rehearsing the necessary dance moves to woe their admirers. Birds that are restricted by the need to find food for survival could never come up with such elaborate, energy-intensive and time-consuming displays. Only in the Birds-of-Paradise does every element come together to allow for the evolution of such splendid creatures. In a very real sense, while the impenetrable jungle of New Guinea many be inhospitable to us, for these birds it truly is a paradise.

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In researching this piece, I relied on work of Sir David Attenborough, Dr Edwin Scholes and Dr Tim Laman.

David Attenborough has had a life long fascination with the Birds-of-Paradise and his numerous documentaries made many ground breaking discoveries concerning their behaviour. For anyone interested, I would recommend the films, Attenborough’s Paradise Birds, and Attenborough in Paradise, as well as his book, The Life of Birds.

Ed Scholes and Tim Laman spent nearly a decade trekking through New Guinea on a mission to record every one of the Birds-of-Paradise on film. They are without doubt the foremost experts on this family of birds. You can find out more about their work through the Birds-of-Paradise Project or their stunning book, Birds of Paradise: revealing the world’s most extraordinary birds.

Notes

[1] Although this number does have a tendency to change from time to time. We will discuss in Part II.
[2] Dimorphism: the difference in appearance of secondary sexual characteristics between males and females of the same species.
[3] There is one exception. Charles Lucien Bonaparte (Napoleon’s nephew) was a famed ornithologist and devoted republican. He didn’t care for the practice of naming these birds after monarchs, so he gave one bird, Wilson’s Bird-of-Paradise*, the scientific name ‘respublica’: the people’s bird.

* The ‘Wilson’ from the common name is for the English ornithologist, Edward Wilson, who had acquired the first specimen of the bird.
[4] Princess Stephanie of Belgium (1864-1945).
[5] Carola of Vasa (1833-1907), princess of Sweden and Queen Consort of Saxony.
[6] Albert of Saxony (1828-1902), Carola’s husband.
[7] Queen Victoria (1819-1901).
[8] Count Francis Raggis of Genoa.
[9] Rudolf, Crown Prince of Austria (1858-1889), Princess Stephanie’s husband.
[10] What that says about European colonialism, I’ll leave you to decide.
[11] In 2016 the Paradise-crow was split into two species, the Paradise-crow and the almost identical looking Obi Paradise-crow.
[12] Some speculated that they were a signal for individuals to recognise members of their own species. As we shall see in Part II, though, this cannot be the case.
[13] The genus Paradisaea contains six species: the Greater, Lesser, Goldie’s, Red and Emperor Birds-of-Paradise. They all have a similar appearance except for some size and colour variations.
[14] The six birds in the genus Paradisaea all display in this way, as does the Standardwing Bird-of-Paradise (Semioptera wallacii).

[15] The Emperor and Red Birds-of-Paradise also display by hanging upside-down.
[16] Something is defined as iridescent when its colour appears to change depending on the angle you look at it from. Think of a soap bubble, or the colourful sheen on the surface of an oil puddle.
[17] It is interesting to note that of the shape morphing birds, the figure that is most favoured is a black oval. The Parotias, the Superb Bird-of-Paradise, the Black-billed Sicklebill and the Rifelbirds all create a similar black oval-like shape when they morph.

[18] The Black Sicklebill does something similar during its display. It rubs its wings together to make a knocking, machine-gun-like sound.
[19] That’s the windpipe which connects the throat to the lungs.
[20] Some have been seen trying to court juvenile males, because at younger ages their plumes resemble those of the females. As we will also discuss in Part II, it means they also don’t always even mate with members of their own species.
[21] Having said this, it should be noted that nearly every Bird-of-Paradise will only lay one egg. That is with the exception of those that form pairs. Manucodes, working as a couple, can raise two chicks at a time.