Profitable Wonders
St James’s Park in early springtime could not have been lovelier.
Diverse pairs of ducks swam contentedly side by side, with a handsome Egyptian goose ushering her newborn chicks to the water’s edge.
Then, thrillingly, two swans – a snowy, white male and a smaller, jet-black, red-billed female – turned towards each other and launched into a balletic courtship waltz.
Round and round they twirled, their long necks intertwined, black draped over white, white over black and then black over white again, for minutes on end. Suddenly, she disappeared, submerged by her more powerful partner at the moment of union.
Resurfacing some yards away, she stood up out of the water, flapped her outstretched wings and sailed away without a backward glance.
‘The courtship rituals of animals are altogether puzzling,’ observed the ethnologist Niko Tinbergen after a professional life spent studying them.
It is certainly difficult to fathom why nature should deploy so extravagant a range of ‘ways’ – performances and posturings, vivid colorations and vocalisations – to achieve the same ‘end’ of sexual reproduction. Though fascinating to observe, those ‘ways’ might be judged unnecessarily over-elaborate – often bizarrely so.
The peacock’s display of its cumbersome, lengthy train is a case in point. The final swirl around is certainly dramatic, confronting the peahen, in all his splendour, with that vibrating arc of iridescent, blue and green feathers. But to what effect?
‘She usually appears to be utterly indifferent, walking away or continuing her quest for food as if her ardent suitor were a hundred miles away,’ writes zoologist William Pycraft in his classic work The Courtship of Animals.
The courtship ritual of the sage grouse is more puzzling still. Every year, both genders congregate at the same place on the windy plateaus of the Rocky Mountains.
Initially, it is only the males, up to 50 of them, who attend. Arriving at first light, they strut up and down for several hours, making a popping sound (‘like a cork being pulled from a bottle’), caused by the inflation and then compression of a large, air-filled sac around the neck.
They then disperse, returning again the following morning. This goes on for a month until, in April, they are joined by females in large numbers who congregate in a dense pack at the centre of the communal display ground.
It’s some glorified ‘coming-out’ ball, you might suppose; an opportunity for the female to select a desirable mate with whom to rear their offspring.
Far from it. Just a handful of unaccountably privileged males get a look-in. Strutting through the female congregation, they have their way with as many as is feasible.
The same performance is repeated every morning for a fortnight, though for 90 per cent of the males their only role is as spectators. As for the females, once ‘serviced’, each one flies off to build a nest where she will lay and incubate her eggs and rear her chicks alone.
The vivid coloration of some, if certainly not all, birds is perhaps more readily explicable. But ‘altogether puzzling’ again is its – at times – exquisite beauty.
‘Picture a bird no bigger than a thrush but of a wonderful cinnabar red, with a gloss as of spun glass,’ writes William Pycraft of the king bird-of-paradise.
He draws attention to the panoply of coloration – an orange-hued head, a white breast crossed by a band of metallic blue, an ivory-yellow beak and legs of cobalt blue.
‘Closer examination reveals yet further points of wonderment,’ he adds. There are green-tipped, fan-like plumes on either shoulder and a pair of tail feathers modified to form slender, ten-inch stalks, ‘coiled like a watch spring and bearing at their ends a disc of emerald green’.
Similar considerations apply to the extravagances of birdsong. Each of the 6,000 species of songbird has its own distinctive melody, of which the musicality’s complexity can verge on the miraculous.
The Australian lyrebird’s astonishing repertoire of 90 different songs incorporates those of many others. In a recital lasting 43 minutes, an ornithologist identified at least 20 that he recognised. The flute-like duets of the East African shrike can be antiphonal (started by one, completed by the other) or polyphonic, including phrases sung in unison or overlapping. What are we to make of this? Scientists, when discussing the nature and origins of the rituals of courtship, talk confidently of ‘reproductive strategies’, ‘inclusive fitness’ or ‘sexual selection’. But how little, pace Niko Tinbergen, we really know.