Natural sunlight, and the angle at which it moves around the earth, drives avian feeding, sleeping, breeding, molting, migration, and other behaviors. Since some of our pet birds spend a majority of their lives indoors, they get minimal exposure to natural light. As such, appropriate indoor lighting can benefit our pet birds.
Birds need ultraviolet (UV) light emitted from the sun. It is UVB light, specifically, that induces Vitamin D production in birds, which helps them absorb calcium and assists in other important bodily functions.
Full-spectrum lights emit light across the entire range of the possible lightbulb spectrum and some contain UVB in amounts beneficial to our avian friends. Because humankind has not, or cannot, compete with nature, we are still unable to exactly replicate the light of the sun. Therefore, no lightbulb can emit light that spans the full ultraviolet, visible, and infrared light spectrum the way that natural sunlight can. However, avian full-spectrum lightbulbs with UVB that are available today better mimic the sun than ever before, thus are well suited for avian care.
So go ahead, bring in the sunshine with full-spectrum lighting.