The Structure and Pigmentation of the Feather Tips of the Scaled Cuckoo (Lepidogrammus cumingi)

Abstract

NU•tEROUS publications have dealt with the study of the structure and function of feathers, their modifications in various groups, and their use as a taxonomic tool (Chandler, 1916). Feather pigments and structural color have received much attention because of their attractiveness and the challenging developmental, biochemical, physical, and functional problems involved (for reviews see Frank, 1939; Fox, 1953; V/51ker, 1960). Terminal structures on the tips of feathers have rarely been studied. Such structures are conspicuous on the secondary remiges of members of the genus Bo.mbycilla, the waxwings. The morphological relations of the pigment and the feather, as well as the nature of the pigment itself, have recently been described by Brush and Allen (1963) for the Cedar Waxwing (B. cedrorum). The morphology of the feather tip of the closely related Bohemian Waxwing (B. garrulus) has also been investigated (Stieda, 1872), and Chandler (1916) concluded that among birds this structure is unique in Bombycilla. However, superficially similar structure may be found in other birds, such as the Paradisaeidae, the birds of paradise. Danforth (1958) reported a feather structure in the male Gray Jungle Fowl (Gallus son-neratii) which resembles that of the waxwing. This study considers the Scaled Cuckoo, Lepidogrammus cumingi, a species confined to the islands of Luzon and Marinduque in the Philippines. Its plumage is not unusual except for the presence of numerous white feathers tipped with black "spangles" which occur on the pterylae of the head and neck. These feathers are the subject of this study. METHODS AND RESULTS Structure.-Entire feather tips from various sections of the bead and neck were prepared as dry mounts and examined microscopically. The tips were also embedded in gelatin, sectioned on a freezing microtome, and mounted in Farrant's solution. Tips were observed both after partial chemical disruption but with internal structure and pigment intact, and as whole tips with the pigment chemically bleached. In feathers with incompletely developed tips, pigment is limited to the rachis and, toward the tips, to several large barbs (Figure 1, A and B). In fully developed tips (Figure 1, C) pigment granules (to the resolution of the light microscope) are, without exception, confined to the tip. Partial bleaching of the pigment revealed that the internal structure of the tip consists of closely packed fibrous tissue, oriented parallel to the long axis. 155 The Auk, 112: 155-160. April, 1965