American Research Journal of Bio Sciences Original Article ISSN-2379-7959 Volume 1, Issue 2, June 2015 www.arjonline.org 21 Structural Variations in Feather Morphology and its Predicted Function in Indian Peacock Pavo Cristatus Monalisa Mishra 1 Asst Professor, NIT Rourkela, Rourkela, Orissa, India Abstract: Peacock exhibit a greate diversity in the morphology of their feather pattern. The diversity of feather changes with age and affect the appearance of peacock significantly. The causes of variations are not known and opens a wide field for scientific research under developmental biology, ecology, ethology and behavioral studies. The current study describes the complete documentation of feathers present in different body parts of peacock (Pavo cristatus) not reported in earlier studies. Keywords: Pavo cristatus, Plumage pattern, Crown feather, Saddle feather, Contour feather, Eye spot, Tail covert. I. INTRODUCTION Feathers produced by birds are extraordinarily diverse and complex in nature 1 . The diversification of feathers arises to congregate numerous physiological and functional requirements of the bird 2-5 . The various functions include flight, swimming, thermoregulation, physical protection, visual and tactile communication, sound production, foraging and water repellency 2,6 . To execute a specific function, feather structures undergo certain changes in size, shape, color, and texture 1,7-9 . In an individual bird various layers of feathers are found in different parts of the body and altogether it forms the complete plumage pattern. Birds develop the most colouful plumage patterns. Each species has its own identifying plumage blueprint 10-13 . As a consequence plumage pattern offers an ideal topic for understanding the process of evolution among birds 14,15 . Intraspecific variation of plumage pattern is observed in many species and such variation is associated with age and sex 16-19 . Sex-linked plumage variation (or sexual dimorphism) is a prominent phenomena among birds, which play a foremost role in avian communication such as mate selection. Earlier sexual dimorphism was focused only on the feather coloration, but later studies have found also its impact on the structural variation among feathers 16,20 . In females, sexual dimorphism arises due to camouflage and instead male develop ornamental feathers. Plumage patterns of male birds are often brightly and diversely coloured although evolutionary cause of this sexual dichromatism is not exactly deciphered 21,22 . The ornamented feathers of male is an indicator of quality, condition, and parental effort which is associated with reproductive success 23 . Plumage colouration in birds can broadly be classified into two types: (1) pigmentary colour (2) structural colour. The first one is the result of chemical properties of pigments 24, 25 and their concentration in feathers, whereas the second one is due to the presence of nanostructures present in it 26, 27 . The most common materials in these nanostructures are keratin, melanin and air 28 . Colours like blue, green, violet and ultraviolet are usually the result of such structural coloration. Plumage colouration, produced by birds covers a wide range of electromagnetic spectrum. Most plumage coloration includes the violet (VS), and ultraviolet sensitive (UVS). To perceive the wide spectral variation of plumage colorations diurnal birds evolve the most advanced color vision 29 . Four different types of cone evolved during eye evolution in birds. Birds use UV cues for mate choice and foraging. The UVS help to discreminate between colours in the natural surroundings. The colour perception of an object/feather depends on three principles 30 : (1) the physics of light reflection and transmission to the surface of the eye; (2) light transmission, reflection and photoreception within the eye; (3) the neural processes in the retina and brain. The second and the third phenomena are associated with the structure of the eye whereas the first one is allied with the structure of the feather. The mechanism involved in the process of plumage colouration helps to understand the evolution of colourful plumage, as various mechanisms have their own impact on the cost of production and maintainance of feather 31,32 . Analyses of feather structure, present in different parts of the body, offer a promising approach to specify how feather structure may mediate life history of an animal 33 . Different types of feather texture indicates that the body plumage has undergone several changes over a period of time independently, making the plumage pattern different 1 Corresponding Author :mishramo@nit-rkl.ac.in