The photonic structure of a barbule is mainly derived from melanosomes, keratin and air and can be arrayed in one-dimensional laminar nanostructures, two-dimensional crystal nanostructures, which may have square or hexagonal lattices, or even three-dimensional nanostructures. 13 The essential characteristic of a photonic crystal is the periodicity of the dielectric material along one or more axes, 14,15 hence they can be one, two or three-dimensional, which is also the basis for their basic division. Photonic structures are seen in many avian taxa and vary within groups of birds that differ in size, behaviour, and ecology. 12 The viewing angle significantly varies the hue and/or intensity of iridescent colours which allows animals and insects to be noticeable to the intended signal receiver, whilst remaining reasonably discrete to avoid conflict with nearby predators. 11 Such colouration is useful for noticeable signals intended for intraspecific communication, sign of warning or flash and startle displays. 10 The uniqueness of structural colours in an organism is due to the selection of one or more different types of nanometric architectures such as single or multi-layer thin-films, diffraction gratings, and photonic crystals, and also due to other physical parameters, such as size and refractive index. 1 Angle-dependent colours often termed iridescent colours are seen in many living species, for example, beetles, 2 dragonflies, 3 butterflies, 4 flies, 5 ducks, 6 peacocks, 7 pigeons, 8 kingfishers, 9 aquatic animals 10 and the plant kingdom. Introduction Structural colours in nature rely on the size and arrangement of physical microscopic structures that exhibit selective reflectance of incident light. Such photonic modulation can be utilized in colour selective filters and sensing devices. The colour shift response of feathers was different in the case of alcohols and other water-based solutions, suggesting different swelling behaviour of keratin against different liquids the water-based solution had the more pronounced effect. The shift in colour was suggested to be due to the swelling of the keratin layer of barbules that absorbed liquids and as a result modified the refractive index and periodicity of the internal photonic structures. A quick reversible change in colours of these feathers was observed when they were soaked in water and other liquids, which reversed upon drying. The feathers exhibited interesting hydrophobic properties, with the dull-coloured proximal end showing lower hydrophobicity with a contact angle between 90° and 110° compared with the iridescent distal end of a feather exhibiting a contact angle between 115° and 120°, attributed to the change in the internal structure and/or density of the feathers.

Sharp changes in the reflected brilliance were observed from the feathers upon changing the illumination conditions, such as horizontal and azimuthal angles. Here, we have studied the internal structure of its feathers from different parts of the bird's body and showed that its beautiful colours and iridescence are due to photonic structures present in the internal structure of the feathers. The bird possesses spectacular iridescent plumage with a range of different metallic colours. Domesticated Yak in Tibetan Himalayas Source: Flickr 7.The Himalayan monal is a bird in the pheasant family, and it is the national bird of Nepal. Maginificiently horned Argali Sheep Source: Flickr 5. A flock of Blue Sheep (Bharel) in the Himalayas Source: Flickr 4. The colorful Himalayan Monal pheasant Source: Wikimedia 3. Giant panda on himalayan mountain Source: Flickr 2.

As you can imagine, these animals are phenomenal in their appearance as well as their mannerisms. Most of these animals are thick skinned, have heavy furs, hooved feet etc. Hence the Himalayan animals have adapted to the climatic and environmental conditions over years of evolution. Mount Everest, it’s cold and snowy throughout the year. Since the Himalayas have some of the highest peaks on earth e.g. these animals cannot be found in any other part of the world. Some of these Himalayan animals are native to the range. Thanks to the massive size of the Himalayas, it’s home to a wide variety of animals. The Himalayas is a mountain range than spans across countries like India, Tibet, China and their neighboring countries.

Himalayan monal pheasant size