Page:The Zoologist, 4th series, vol 5 (1901).djvu/412

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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