The Zoo Med Avian Sun 5.0 UVB compact fluorescent provides birds with safe levels of beneficial UVB and UVA for physical and psychological health. UVB enables birds to synthesize vitamin D3 for proper calcium metabolism which is necessary for normal growth, maintenance of strong bones, and egg production. UVA is visible to birds, enabling them to recognize mates, locate food, and identify different species. Without UVA, birds are essentially colorblind! These Avian Sun 5.0 UVB and UVA bulbs cannot be used with dimmers or rheostats!