For all the enchantment the color blue has cast upon humanity, no animal has fallen under its spell more hopelessly than the bowerbird, whose very survival hinges on blue.

In a small clearing on the forest floor, the male weaves twigs and branches into an elaborate bower, which he decorates exclusively with blue objects — the blue tail-feathers of parakeets, blue flowers and berries, bones and shells so bleached by sun and sea as to appear bluish-white, and, in the past century, various souvenirs from the waste and want of our own species: blue plastic caps, blue candy wrappers, blue strings. These he arranges on a straw platform in the front, where he performs his ecstatic courtship dance whenever a female enters the bower to consider him as a mate.

Unlike the octopus, capable of seeing shades of blue we cannot conceive, bowerbirds have been found to have no optical advantage in perceiving this particular color — they appear simply to like it. It may have to do with how much more impressive it renders the male’s feat: Although we live on a Pale Blue Dot — the consequence of an atmosphere that bends sunlight to make the oceans blue — blue is the rarest color in the living world. Humans have waged wars over indigo and traded fortunes for lapis lazuli. Perhaps the bowerbird recognizes that no color is more precious than blue, and therefore none is more seductive — seduction so ornate and labor-intensive because the stakes of mating are so high: most bowerbird pairings are monogamous, produce very few eggs of enormous size relative to the bird, sometimes just a single one, and the males take an active part in rearing the chicks.

When the taxidermist turned zoological writer John Gould first popularized bowerbirds in the 1840s in his landmark book on the birds of Australia — rendered a bestseller largely thanks to the 600 consummately illustrated plates by his gifted and tragically fated wife Elizabeth — the purpose of the bowers was still a mystery. Watching both sexes “run through and around the bower in a sportive and playful manner,” he deduced that, contrary to what the first Western observers had assumed, these fanciful structures “are certainly not used as a nest,” but he could not discern their exact purpose. Some naturalists went as far as speculating they were “play-houses” the birds built simply to amuse themselves.

But within a quarter century, as theories of sexual selection cast a new light on the living world, Darwin — who regarded the bowers as “the most wonderful instances of bird-architecture yet discovered” — was able to conclude that they are the bowerbirds’ theater “for performing their love-antics,” built “for the sole purpose of courtship.”

In his landmark 1871 book The Descent of Man, and Selection in Relation to Sex, Darwin quotes an observer’s delightful account of what actually happens in this theater of blue:

At times the male will chase the female all over the aviary, then go to the bower, pick up a gay feather or a large leaf, utter a curious kind of note, set all his feathers erect, run round the bower and become so excited that his eyes appear ready to start from his head; he continues opening first one wing then the other, uttering a low, whistling note, and, like the domestic cock, seems to be picking up something from the ground, until at last the female goes gently towards him.

An epoch later, we know that the bowers are part of the bird’s extended phenotype — a term Richard Dawkins coined in 1982 to describe the genetically determined observable characteristics of an organism that extend beyond its body and into its behavior, affecting its environment and ecosystem. A beaver’s dam, which changes the course of rivers and the lives of myriad other animals, is part of the beaver’s extended phenotype. A city is part of ours, as is language. (Out of the extended phenotype arose the notion of the extended mind.)

Of the twenty known bowerbird species, all native to Australia and New Guinea, none is more aesthetically impressive than the Satin Bowerbird (Ptilonorhynchus violaceus) of eastern and south-eastern Australia. The male — himself a living artwork with deep indigo plumage that shimmers like satin, wing-feathers of velvety black, a bright ivory-yellow beak, and otherworldly purple eyes — builds what is known as an avenue bower: a short corridor of twigs with opening at both ends, facing the veranda of blue.

But what makes these cathedrals of courtship especially wondrous is the conceptual centerpiece of their design: female consent and freedom of choice.

When a female enters the bower from the back, the male commences his hopeful dance of desire, fluffing out his wings and body feathers, occasionally picking up a blue object, holding it up to the female, and cocking his head as if to say, Isn’t this beautiful? Aren’t I a catch for knowing beauty? If she is sufficiently impressed, she remains in the bower and crouches into a low copulating posture, inviting him to circle around and mount her. If she finds him lacking, she simply walks through and exits, proceeding with her search for a mate of greater virtuosity in blue. After all this labor, the rejected male is left as living affirmation of Rebecca Solnit’s haunting rendering of blue as “the color of solitude and of desire.”

Donika Kelly animates the bowerbird’s plight of bittersweet beauty in a poem — that exquisite extended phenotype of the human species — from her altogether magnificent collection Bestiary (public library):

BOWER
by Donika Kelly

Consider the bowerbird and his obsession
of blue, and then the island light, the acacia,
the grounded beasts. Here, the iron smell of blood,
the sweet marrow, fields of grass and bone.

And there, the bowerbird.
Watch as he manicures his lawn, puts in all places
a bit of blue, a turning leaf. And then,
how the female finds him,
lacking. All that blue for nothing.

Complement with Maggie Nelson’s stunning ode to blue, then revisit the wonder of hummingbirds hovering between science and magic.