AUBREY EDWARDS:  

As a field naturalist in a small way I wish to bring to the notice of the Members of this Natural History Field Club the wonderful night-soaring habit of the Swifts.

I will take it that my fellow-members are well acquainted with this bird Cypselus apus of the family Cypselidae of the order Picariae, except as to its habit of roosting in the sky, which was first discovered by my brother, Cyril Edwards (now Rector of Mottisfont, in Hampshire), and myself in 1886, and published by me in a letter to Nature of October 27, 1887.

My excuse for bringing this matter before you is that, though it has been published as just mentioned in 1887 and later in the Selborne Society's Magazine in 1890, January -May, and by Mr. Wichell in Knowledge, June 1, 1897, and often noticed in short paragraphs in The Field, and again by myself in a lecture to the Bournemouth Natural Science Society in December, 1912, very few people have heard of it, and fewer still believe it. And it is not everyone who has the opportunity of observing it. In a Field Club like this I feel sure there will be some who can and will investigate this most wonderful exhibition of wingmanship of this merry and wonderful bird.

I can take it for granted that you all know that the Swift has nothing to do with the swallow, but is a relation of the nightjar and the hummingbird. That it is a dark olive brown bird (with a white chin), weighing 1½ oz. and measuring 7½ in. in length, with the comparatively enormous stretch of wing of 15½ inches. That its four claws all point forward and are very sharp, that the sole of the foot extends to the joint above, and you might call the bird plantigrade. That the foot is designed for clinging on to rocks and walls. That the bird cannot sit on a bough; it can only lie along a ledge. That the shape of the body is like a slightly flattened fish, with perfect streamlines and nothing projecting to catch the wind. That the bird does not seem to bend the last joint of its wings in flight, but always keeps them widely stretched, never folded back like those of the swallow. That its dark brown eye is deeply set with an embrasure cut out so that the bird can see straight ahead. That it arrives in pairs in the first week in May and leaves about the 11th of August - the last to come and the first to go. That it pairs for life, and comes back to the same nest year after year. That its one note is a shrill scream, which, when uttered in chorus as the birds are flying round in rings, is the most joyous of all the birdsongs in this land. You will know that, in spite of what all the bird books say, the Swift, if unwounded and in good health, can rise from the level ground if it has headroom and is not soaked in long, wet grass. That it never settles on the ground or at any other place than its own nest, except when it is exploring for a nesting-place. That it does everything in the air except make its nest, lay its eggs, incubate, and feed its young. That it eats, drinks, mates, and gathers materials for its nest on the wing.

That it roosts on the wing, I am not taking for granted that you know.

But if you have lived a few yards from a Church where many pairs of Swifts nested, and have studied them for the best part of your life, and have read Gilbert White's monograph on the Swift in his Natural History of Selborne, you will know that the eggs - two or sometimes three - take 19 to 21 days to hatch, and that the young, which are blind for nine days, take six weeks to reach maturity. That they remain in the nest, never leaving it till they fly to Africa - probably without resting. That these and all other summer migrants come here only to breed, and leave as soon as the young are ready to fly; and that, unlike the swallows, the Swifts have only one brood. That the hen alone tends the young. That its nest is bound together by the glutinous saliva of the Swift. And doubtless, if you have had my opportunities, you have, when you realized the difficulty they have in procuring materials in the air, scattered feathers from the soundholes and watched them race for these, and noted how, though not a Swift was in sight at first, soon the air was full of the dark forms capturing feather after feather till they seemed to have long white moustaches streaming out on each side. And when you have been watching up amongst the bells in the church tower, and taking notes of dates day after day, you may have been set back a whole-year by a wretched mouse killing the bird you were watching to ascertain its rate of growth. You will know what beautiful glossy birds the young ones are, with their quill feathers edged with light and with their pink feet. You will know that the Swift can fast for a long time, but that cold weather numbs and eventually kills it. That its food consists ex­clusively of winged insects, which it cannot take except in the air, as it is too highly specialized to be able to pick a fly off a window. You will know what merry and playful birds they are, and that they have been evolved for a life in the air.

I thought the members might like to be reminded of a few of the interesting facts they know about the Swifts before coming to the point of this paper - The Night-soaring of the Swifts.

If you will watch the Swifts at sunset on a fine evening you will see them all gather together and fly about in all directions, like distracted spirits, for some time. Then, as the dusk creeps on, you will see them get into order, form them­selves into a flock, and ascend into the sky in wide spirals, screaming all the time. They will disappear from sight several times, but come round again, and at last they will rise so high that they are lost to the sight of the unaided eye, though with a binocular you can see them for some minutes longer. Then the sound ceases, and the stars are out.

If after watching them up you had sat on a tombstone under the eaves where they build, till half-past ten (with watchers on the other side of the church) to make sure that no bird returned to the nests, and on other nights alone till eleven, you would know each time that they didn't come back to their nests that night.

At first - say till the first of June - all the birds go up together, but when the eggs are laid the hen stays at home ; and a male bird may often be seen driving a late-flying hen back to the nest before he goes up with the others. Mr. W. A. Wichell, the author of The Evolution of Bird Song, pointed out the meaning of this performance to me - the swoop of the one bird at the other and the escape of the latter, who, however, is always brought back to the nest at last. White of Selborne notices that the hens come out to feed in the evening. I proved this by cutting some of their tails square.

There is no question that the Swifts go up into the air out of sight on a fine night, and that they stay away till the morning ; but what proof is there that they remain on the wing ?

Though convinced that they do, I cannot prove it, and, though I have watched them up a hundred times, I have never seen them come down again.

But a farm boy to whom Mr. W. H. Hudson was talking, near Wells, told him that they remained flying about all night, and that he had often seen them rush straight down as if falling from the sky at the same place soon after sunrise, when he was crow-scaring. This is told in "Nature in Downland," and the boy said that he had found it out for himself. And Mr. Edward Hart, of the Bird Museum at Christchurch, tells me that he also found out some 14 or 15 years ago that the Swifts ascend and spend the night in the air, and that he has counted them up at sunset and counted them down at sunrise.

That is as near as I can get to proof.

If anyone should say "They go and roost at a distance" I can only reply, "Why should they? Why should they go and roost in distant cliffs - which is the only reasonable suggestion that can be made - when they have their own snug nests at hand, in which they do rest when the night is not fine enough for them to ascend?" Many a time have I watched them make a trial trip and then come down again and go into their own proper nests because the weather was not good enough.

Of course it is no question of food. I believe it is sheer delight in their strength of wing which sends them up. And, as for keeping there, very little exertion would be required for a Swift to balance itself with its head to the wind during a summer night.

Roosting in the sky is quite an easy matter for the Swifts. The difficulty is in people believing it.

I hope the members of this Field Club who have the opportunity will investigate the matter.

(Printed 1914 in Proceedings of the Dorset Natural History and Antiquarian Field Club.)

© APUSlife 2004, No. 2953

ISSN 1438-2261