As humans we see three primary colours (red, blue, and green) which combine to give us the images we see all around us. A bird however can see a further into the blue range (ultra-violet) which gives them a very different view of the world. UV markings are present in the birds plumage and are used to indicate many different things. Therefore if a bird does not recieve UV light then an important part of its vision is lost. Captive birds can recieve this UV in one of two ways; either through exposure to direct sunlight (not via a window which filters out UV) or from an artificial light source such as the Bird Lamp which contains the required UV as well as the visual content. In addition the UV light is used by the birds to synthesise vitamin D3 within their feathers.