The Zoologist/4th series, vol 5 (1901)/Issue 724/Breeding Habits of the Swift, Ellison

by Allan Ellison

 

BREEDING HABITS OF THE SWIFT.

By the Rev. Allan Ellison.

 

I have been much interested by the Rev. F.C.R. Jourdain's article on this subject (ante, p. 286), and especially by the evidence he brings forward upon the question as to the number of eggs produced at a laying by these birds. How there ever has been a controversy on this point is a puzzle to me, unless it be that comparatively few observers have examined any great number of the nests of the Swift, owing to the difficulty of getting at the places where they build.

In days gone by I had unusual facilities for investigating the breeding habits of the Swift, as a large colony nested in crevices under the eaves of some tall buildings to which I had free access. I examined some dozens of their nests, and found three eggs to be quite a usual number—I should say, more usual than two. The experience of Mr. R.J. Ussher ('Birds of Ireland,' p. 103) agrees with this. The suggestion that when three eggs are found, they are the produce of more than one female, is, I think, untenable. Far more probably, in many cases where but two are found, one of the eggs has been destroyed, or dropped away from home. Mr. Jourdain has mentioned that broken eggs have frequently been found under the nesting-places, showing that eggs sometimes roll out of the nests. This is a thing very likely to occur, as the nest of the Swift is generally a very slight affair—saucer-shaped or almost flat. I have once found the eggs resting on the bare stone, with only a slight ring of nesting materials round them. In the case of almost any bird's nest, it is not unusual for one or more of the eggs belonging to the clutch to be missing. Thus I have found the nest of a Long-eared Owl with but one egg, nearly ready to hatch, though that bird lays five or six eggs. The explanation was soon found, however, for in the same wood there was the nest of a pair of Hooded Crows with the bird hatching.

The well-known fact that Sparrows often quarrel with the Swifts over the possession of the nesting-holes will account for many an egg being knocked out of the nests. I have also noticed that the Swifts themselves, when disturbed, have a habit of fluttering and scrambling about in their nesting-holes, so that eggs may sometimes be dislodged by the parent birds.

The question also occurs—Are birds which nest in deep holes or crevices known to lay in each other's nests? This takes place most usually in the case of birds which make open nests on the ground, especially those which breed in colonies, as Gulls or Terns; also in the case of Game-Birds, as Partridges or Pheasants; and Water-Birds of various species, as Ducks, Coots, Moor-hens, &c. It certainly occurs less frequently with those which build their nests in trees or bushes, as do most Passerine birds; and, I should say, very rarely, if at all, in the case of birds which nest in holes. This, however, is a subject upon which further investigation is desirable.

The nesting materials which Mr. Jourdain mentions as used by the Swift agree entirely with my own experience. Feathers, small straws, and pieces of rubbish are always found—just such materials as would be blown into the air on windy days; but I have also generally found a quantity of the blossoms, catkins, or bud-scales of various trees, especially those of the oak and beech, which are blossoming just at the time when the Swifts are building, and whose blossoms are frequently blown about by the strong breezes of the end of May. These materials are always cemented together by a glutinous substance secreted by the bird. Indeed, without this curious provision of nature, the scanty materials could hardly be woven together into a nest at all; and it is no doubt intended to keep the substance of the nest from being dispersed, as the Swift generally builds in a large and irregular crevice, and is not able to lay down a large bed of materials filling the entire bottom of the hole, after the manner of the Tits or the Creeper; nor, as in the case of the Sand-Martin, would the loose feathers and straws be held together by being placed in a small and comfortable space.

There is no doubt a good deal yet to be learned about the nesting habits of these interesting birds, for the difficulty of observing them is very great, owing to their breeding in dark holes and crevices out of sight, and often in rather inaccessible situations.