OCR Text |
Show 1896.] METALLIC COLOURS OF BIRDS. 291 this apical band, until such a metallic feather as that of fig. 1 is produced. The course of development of the metallic edging of quill-feathers may be described in a little more detail. In order to illustrate this, it may be convenient to describe in a concrete example the differences between the sexes in the coloration of wings and tail. The following notes were made on a female of Anthreptes malaccensis and a male in nearly completed moult, but the characters of the adult male were checked by reference to Shelley's ' Monograph of the Sun-birds.' In the male the tail was composed of black feathers with an edging of metallic violet, which was widest in the case of the two central feathers. In the wings the lesser wing-coverts had a broad transverse band of metallic violet, the median coverts a similar band of dark brown, and the greater coverts a longitudinal band of olive-yellow, which becomes brown in a completely adult male. The wing-quills themselves were greyish brown with olive edges. In the female the tail was dark brown with an edging of olive-yellow. The wing-quills and wing-coverts were ashy grey with longitudinal or transverse bands of olive-yellow distributed in the same way as in the male. In the female the general contour-feathers had a broad transverse band of olive-yellow, while in the male most of these feathers had been replaced by others with transverse metallic bands. It must be noted that in all these cases the olive-yellow part of the feather has a peculiar looseness of structure visible even to the unaided eye. It should also be observed that the yellow edging to the quills is seen both in the rectrices and remiges of the female in this as in numerous other Sun-birds, wiiile in the male the edging is replaced in the case of the rectrices by a metallic band. The respective distributions of longitudinal and transverse bands should be especially noticed, as showing how very closely the nature of the stripe depends upon the nature of the feather, that is upon its elongation. From the above description it is obvious that some sort of relation exists between the olive-yellow margins of the feathers of the female and the metallic margins of the feathers of the male. In general, w e m a y say that there is a tendency for the feathers with olive margins in the female to be replaced by feathers with metallic margins in the male. It will be noticed that the change is associated with increased pigmentation in the male; in the median wing-coverts there is only slightly increased pigmentation without metallic colour. Such a tendency is very widely spread in the family, but the extent of replacement differs greatly. Thus in the species described above the olive edging of the greater wing-coverts and wing-quills is not replaced by a metallic edging in the male. In Nectarinia famosa an olive edging in the same feathers in the female is replaced in the male by a metalhc edging. In Anthrobaphes violacea the tail-coverts are edged with yellow in the female and in most males : according to Shelley, some males as an individual variation have this edging metallic. It is, however, needless to multiply examples. Enough has been said to justify 19* |