My understanding is that most windows in homes block UV light, so putting your bird in sunlight from a window provides nothing but warmth (& entertainment, if they can look outside the window!).
Look into full spectrum lighting more, & you can see there are a lot of factors associated w/it. Too far from your bird & it's no longer beneficial. Too close & it's hot, or some say can hurt your birds' eyes. I have one because I'm a better safe than sorry kind of person, but I focus my energies on trying to get my birds outside for a bit every day.
oh, & I don't have an aviary (although the plan is to have one by spring 2013!). Just use your travel cage w/some water & a few toys!







