Page:The Zoologist, 4th series, vol 3 (1899).djvu/161

Rh one of last year's birds from Norfolk.— (54, London Street, Reading).

Fecundity in Birds.—Respecting Mr. Basil Davies's very interesting article on the Fecundity in Birds ('The Zoologist,' 1898, p. 495) I should like, if I may, to make a few remarks, and to ask some questions, hoping that Mr. Davies will not resent the liberty I am taking in doing so. In Section I. (dealing with Finches, Buntings, and the larger Warblers) he writes:—"It is not, I think, difficult to see why they respectively lay their five and ten eggs a season. These birds, resident and migratory alike, feed their young on various forms of insect-life.... The two parents would be unequal to catering for the wants of a larger brood than five. Neither could a hen of this size well produce more than five eggs." Now, the fact that insectivorous birds can rear a considerably larger brood than five is clearly demonstrated by the Tits, Wrens, and small Warblers (Chiffchaff, &c), as is also the fact that a bird of half the size of a Bunting can and does produce more than five eggs. Lower down, in Section II., he writes:—"Another point is that eight young Tits would hardly require more food that five greedy little Robins, and so the labours of the parents in the two species would not differ appreciably." And again, in discussing the smaller Warblers:—"Here again it is no more difficult to feed eight small Warblers than five large ones." Now, it seems to me that, though ten young Golden-crested Wrens (for instance) might not require altogether a greater quantity of food than five young Robins, yet, as the minuteness of the food would be in proportion to the smallness of the bird, each young Gold-crest would require to be fed the same number of times a day with gnats as a young Robin would with caterpillars (or even more); therefore the ten of them would give their parents twice as much work to do as would the five young Robins. In the introduction to Col. Montagu's 'Dictionary of British Birds' an account is given of a female Gold-crest feeding its eight young ones, which were placed in a cage upon the window-sill. The bird brought food every one and a half to two minutes during sixteen hours of the day. A friend once timed a Robin to and from its young, and found that there was an interval of about ten minutes between the visits. So that, as far as catering powers are concerned, it would seem that a Robin might easily rear more that five young ones. Mr. Davies suggests that our migratory Warblers do not produce a second brood, owing to the near approach of the migration period. This argument is broken down by the Swallow kind, all of which produce a second brood. In Section VI., on Doves and Pigeons, Mr. Davies says:—"I have only the old hackneyed explanation for the unvarying pair of