Page:The Zoologist, 4th series, vol 6 (1902).djvu/304

254 before it has lost all its structurally youthful characters, the bill of the nestling bird not having been perfectly modified into the long slender form of the fully matured male.

I have written so many short articles upon the sexing of birds by external characters, that I feel it would be superfluous to go again over the whole ground. I will therefore confine myself to a few general suggestions, which may be useful as guides to the student of this subject. There maybe exceptions to the general rules, because my studies have necessarily been confined to a comparatively small number of species; and, moreover, there are still many families of birds which I have not examined; so that, even if my distinctions should prove constant to all members of a family, much yet remains to be done.

So far as I have had an opportunity of testing sexual characters, I believe that among flying birds, in which the male is dominant, the primaries of the male are longer than those of the female, or, at any rate, the wing from its base to the end of the longest primary shows greater length.

In the Thrushes (Turdidæ), I believe it will be found to be the rule that the entire body is longer in the male, the skull and bill longer and narrower. In the Liotriges the adult males are rather larger than the females, with their bills slightly, but very slightly, broader. In the Bulbuls the same differences occur, but they are more pronounced. In the Tanagers I believe the culmen of the upper mandible in adult cock birds is generally more arched, but the difference is not very marked, and young males in full colour show it less clearly than old birds. However, the sexes of Tanagers generally differ somewhat in colour, even the Superb Tanager (Calliste fastuosa) not being difficult to sex when fully adult. The sexes of Finches differ as regards the form of their beaks according to their habits, so that no general rule can be laid down for them; the males are usually larger than the females, and have longer wings. The Crows (Corvidæ) have broader and stronger bills in the males than in the females. The so-called Piping Crows (Gymnorhina) have longer and more slender bills in the males. The males of Larks are broader in chest, are altogether larger, and have longer wings than the females. The Parrots (according to the late Mr. Abrahams) have a much more rounded blunter infero-posterior angle to the