Down feather morphology of select avians from the Philippines

The microstructure of down feathers from six genetic groups of Philippine native chickens (Gallus gallus domesticus: g.g. Banaba, Boholan, Camarines, Jooanon and Indus) and six species of hornbills from the Philippines were described for taxonomic significance, identification purposes and establishing baselines for future use. The node morphology (shape and symmetry), pigment location and distribution, barbules measurements of the down feather were determined using a light microscope with attached camera. The node shapes exhibited were expanded node (native chickens, Haliastur indus), spine (native chickens, P. jefferyi), prong (Heliaeetus leucogaster and all hornbills) or ring (female Boholano and female Camarines) which are mostly asymmetrical. All hornbill species were observed with intermodal or abundant pigment distribution. Sexual dimorphism was observed in the prong angles of male P. jefferyi and H. leucogaster individuals, wherein the males had wider mean prong angles compared to females. The pigments of all avians studied are mostly located prenodally except for B. hydrocorax, R. leucocephalus, and A. marchei which had postnodal pigment location but distribution varied from absent to abundant. Female H. leucogaster had the shortest barbule (2.07 mm) while female Anthracoceros marchei had the longest barbules at 4.04 mm. On the other hand, the mean number of nodes per barbules is least in female H. leucogaster (21) and the most number in male Banaba (55). The phenotypic description would complement other morphological descriptions and genotypic studies of the same species of avians. The knowledge of down feather characteristics will be used for animal identification especially in cases where no other body parts are present for proper identification. This is useful in taxonomy, trade, bird strikes, biomonitor, textile industry, prey-predator relationship, archaeology and mechanism for host-specialization of skin parasites.