As Oiraons evolved and adapted to their new environment, they were able to thrive in many different biomes.  To simplify, we classify the biomes into 5 types: Arctic, Water, Forest, Desert and Mountain. Here is a reference to the adaptations the Oiraons took on as they evolved, though, you do not need to follow these body types strictly when designing your Oiraon.  Additionally, hybrids may occur in the species, that means a mix of two biomes, the hybrid offspring will have a mix of both the parent's body types.  An example would be a cross between an Arctic and Water Oiraon.  The offspring may possess the sleek, waterproof feathers of the Water Oiraon with the density and insulation ability of the Arctic Oiraon.  They may also be larger in size with thicker feather coverage, but less so than a full Arctic Oiraon.