To ordinary observers a Swift appears so much like a Swallow, that the only difference discernible by them is a difference of colour. To the inquiring naturalist, however, a much more important distinction presents itself in the peculiar and remarkable anatomy of the former bird. Not only has it a greater extent of wing, moved by larger and more powerful muscles, but the structure of the foot is curiously adapted for climbing within the narrow crevices which are usually selected as nesting-places. In the Swallow and other Hirundines the toes are long and slender—three in front and one behind in the same plane, as is usual with insessorial birds. In the Swift we find the toes short and stout, and all four directed forwards; the least toe (which should be the hind one) consisting of a single bone, and the other three of only two bones apiece—a peculiar construction, but well adapted for the purposes for which the feet are employed.

This singularity of structure has induced naturalists to consider the Swifts (for there are several species) generically distinct from the Swallows; and the former, therefore, are now placed by common consent in the genus Cypselus, a name adopted from Aristotle, and suggested by Illiger, as indicating the bird’s habit of hiding its nest in a hole.

The remarks which have been made upon food in the case of the Swallows, apply equally in the case of the Swifts. The latter have so frequently been observed in localities presenting very different species of insects, and sweeping in the summer evenings through the midst of little congregated parties of various kinds, that there is little doubt that the nature of the food differs very considerably. In corroboration of this it has been shown that anglers have repeatedly captured these birds with artificial trout-flies of very different appearance.[76] Isaak Walton informs us that Swifts were in his time taken in Italy with rod and line; and, according to Washington Irving, one of the sports of the Alhambra was angling for swallows from its lofty towers.[77] There are several species of Swifts distributed throughout the world, but only two visit the British Islands, and of these one is but a rare and accidental visitant.

The Common Swift is the last of the Hirundines to arrive in this country, and the first to leave it. Its habits are very different from those of the Swallows. As a rule it makes no nest, but only lines a hole, into which it creeps; it lays but two eggs (rarely three), instead of five or six like the Swallows; it rears but one brood in the summer, instead of two, or even three, as Swallows often do. The late Mr. J. D. Salmon described[78] some nests of the Swift which he found at Stoke Ferry, Norfolk, and which were composed of bits of straw and dry grass, “closely interwoven and held firmly together by an adhesive substance very much resembling glue, and so disposed round the inner edge of the nest as to hold the straws in their places; the whole forming quite a cup of an oval shape, of about four inches in length, not very deep.” I have often observed the straw and dry grass, with the addition of feathers, but never noticed the “adhesive substance.” Gilbert White thought that the Swift paired on the wing. They may do so occasionally; but, from what I have observed, I feel sure that they pair much oftener in the hole which has been selected to nest in.

Although usually preferring lofty towers and church turrets, the Swift frequently nests under eaves at a comparatively short distance from the ground; and I have had excellent opportunities for some years past of observing Swifts during the breeding season under the eaves of some old cottages in Sussex and Middlesex. By means of a short ladder I have been enabled to inspect many nests both before and after the young were hatched; and, out of a score or more examined, seldom more than one contained three eggs. Sometimes I observed that Sparrows were ejected and their nests appropriated, amidst much remonstrance and screaming; but, as a rule, I have found that Swifts, having once reared their young safely in a new locality, will return to the same hole year after year. Birds have been marked by having their claws cut, and, on being set at liberty, were caught the following year in the holes from which they had first been taken. Unlike most insectivorous birds, which bring but a single insect (or at most two or three) to the nest at a time, the Swift visits its young less frequently in the day, but brings a large store at each visit. The mouth is often so crammed with small black flies, that the bird presents the appearance of having a pouch under the chin, from which it ejects the insects in a lump the size of a boy’s marble.

As a general rule, the Swift is not observed in this country before the third week in May, and is seldom seen after the third week in August. It is found throughout the mainland of the British Islands, and breeds also in Mull and Iona, but not in Orkney or Shetland, nor in the Outer Hebrides. It does not travel quite so far north as either the Chimney Swallow or the Martin, but the late Mr. Wolley saw it on the Faroes,[79] and Mr. Wheelwright frequently observed it hawking over the high fells at Quickjock, Lapland, during the summer.[80]

If we look for the bird during the months that it is absent from Great Britain, we find that it is very abundant at the Cape of Good Hope in winter, arriving about September 5, and departing northwards in April. It is seen in Natal more or less all the year round, but more plentifully during the summer.[81] The climate of Lower Egypt is apparently too cold for this species in winter, but at that season it is resident and abundant in Upper Egypt.[82]

As winter disappears it gradually moves northward, and a month before it arrives in England it is found in some numbers along the entire coast-line of the Mediterranean. Mr. Osbert Salvin saw it at Tunis on the 8th March, and subsequently numerous at Algiers. In the middle of March, Mr. Chambers found it plentiful at Tripoli, and at the end of the same month it was observed by Mr. Howard Saunders at Gibraltar. In the middle of April, Lord Lilford remarked that it was common in the neighbourhood of Madrid; about which time, according to Messrs. Elwes and Buckley (“Ibis,” 1870, p. 200), it usually makes its appearance in Turkey, arriving there doubtless from the Ionian Islands,[83] Egypt and Palestine, where it is said to appear in the last week of March.[84]

From Spain, through France, to England is but a short journey for a bird with powers of wing like the Swift; and hence one is not surprised to see hawking over the South Downs in May the birds which but a week previously were circling round the Moorish towers of Spain. Its return southward in autumn is apparently by the same route as that chosen for its northward journey in spring, and in this respect it differs in habit from many other species.[85]

In India its place is to a certain extent taken by a non-migratory species, Cypselus affinis, but it has nevertheless been met with in that country. An Indian specimen was received from Dr. Jerdon, presumably from the north-west.[86] It has also been forwarded from Afghanistan,[87] and Dr. Stoliczka found it at Leh, in Western Thibet. I am aware that some naturalists have expressed doubts as to the identity of the Swift found at the Cape of Good Hope with Cypselus apus; but, after an examination of several examples of the African bird, I have been unable to discover that it differs in any material respect from our well-known summer migrant.