Birds in Flight

by W. P. Pycraft

Among our native birds, the only other species which habitually, and especially during the courting season, produce characteristic sounds during flight, by bringing the wings smartly together over the back, is the night-jar. But there are certain small passerine birds, known as mannikins, inhabiting the forests of South America, which have the shafts of the quill-feathers of the fore-arm enormously thickened. By means of these transformed and translated “castenets,” at will, the bird can produce a sound which has been likened to the crack of a whip.

So far this discourse has been concerned solely with “courtship” flights, or flights associated with peculiar sounds, dependent on rapid movements of the wing in mid-air for their production. And with the mention of these instances this Chapter might, quite legitimately, be brought to an end. But it must not. And this, because there are a number of birds which put their wings, during Courtship season, to very different purposes. Spectacular flights and evolutions in mid-air do not appeal to them. They use their wings instead as lures, as a means of adding intensity to strange poses and pirouettings; whereby they desire to give expression to the amorous feelings which possess them, in the hope—if for the moment, we may accord to them human standards of intention—of arousing kindred emotions in their mates.

Darwin was the first to draw attention to these curious displays. Which, on the evidence then available, seemed always to be made, and only to be made, by birds having wings conspicuously coloured. It seemed as though the possessors of such wings were conscious of their beauty, and so displayed them that nothing of their glory should be missed.

The sun-bittern affords a case in point. This bird, a native of Brazil, is soberly, but very beautifully coloured when at rest; its plumage presenting an indescribable mixture of black, grey, brown, bay, and white; blended in the form of spots, bars, and mottlings. But during times of sexual excitement it will spread out its wings in the form of a great fan, encircling the long, slender, neck. And in this position they present a very conspicuous appearance, taking the form of beautifully graded bands of black, white, and bright grey, forming patterns which vanish the moment the primaries fall into their place behind the quills of the fore-arm. But when thus spread the bird seems to find the greatest delight in displaying their chaste splendour before his mate. He seems to spread his wings just because he is conscious of their beauty when thus opened out.

But we need not travel so far as Brazil to find examples of displays of this kind. Among the birds of our own Islands we can find many close parallels. The chaffinch and the goldfinch, when seeking to arouse the sympathy of their mates make much play with their wings, not only in short “nuptial flights,” designed, apparently, to display the conspicuous and brilliant colouring of the plumage as a whole, but when perched on some convenient spray. At such times the wing is more or less completely spread out, as if to reveal, to the fullest possible advantage, the bright bars and splashes of colour which this extension alone can bring into being.

Since these gaily coloured vestments seemed always to be associated with striking, stilted, attitudes, sometimes bordering on the grotesque, and always to be paraded in the presence of the female, Darwin drew the inference that they were the outcome of female choice persistently exercised during long generations. That is to say he held that, far back in the history of the race, these performers were soberly clad, as their mates commonly are. Then certain of the males of these now resplendent species began to develop patches of colour, small at first, but gradually increasing, generation by generation, in area and intensity. This progressive splendour, he believed, was due to the “selective” action of the females, which, from the very first, chose from among their suitors those who stood out among their fellows by reason of their brighter plumage. Thus the duller coloured males died without offspring. On this assumption each succeeding generation would be, in some slight degree, brighter than the last, until the process of transformation ended in the glorified creatures we so admire to-day.

It would be foreign to the purpose of this book to pursue this theme at length. Let it suffice to say that while the “Sexual Selection” theory still holds good, it has, so to speak, changed its complexion. And this largely owing to the accumulation of new facts. For the most important of these we are indebted to the singularly exact and laborious observations analysed, clarified, and interpreted with remarkable insight and sagacity of Mr. H. Eliot Howard, one of the keenest Ornithologists of our time. He has set forth his case, and interpreted his facts with masterly skill, and there seems no escape from his conclusions. Briefly, he has shown that birds of quite sober coloration like the warblers, which formed the basis of his investigations, engage in displays quite as remarkable, and of precisely the same character as in birds of gaily coloured plumage. From this it is clear that this wing-play is not prompted by a more or less conscious desire to display conspicuously coloured patches of colour, for of colour there is none save that of the general hue of varying shades of brown, as in the case of the grasshopper warbler, for example. Nor is the display, apart from colour, to be regarded as a performance slowly perfected through long generations through the selection of females, coy and hard to please. We must regard these “Nuptial flights” and wing-displays, as the outward and visible signs of a state of ecstatic amorousness on the part of the males which, by their persistence and frequent recurrence, at last arouse sympathetic response in the females. They play the part of an aphrodisiac. Without them there would be no mating. In my “Courtship of Animals” those who will may pursue this subject further.

Herons