Well, there are almost no studies on parrots and, as far as I know, none on light but there are myriad studies on other avian species as well as lots and lots and lots on light and chickens (because of the industry, of course, and the fact that most chickens are raised indoors). So, yes, there is empirical evidence that light quality affects both the endocrine and the immune system in birds.
As to the Swiffer experiment in your house, you have more guts than I do because I would never, ever, ever experiment on any of my animals. Mind you, I am not saying that you are not right in the no-effect conclusion, you might very well be! But, personally, I don't know how you can possibly determine this with any degree of certainty because, when it comes to birds' respiratory system, two years are not what one would call proof of anything... I mean, there are birds that have been breathing in second hand smoke for longer than two years without actually showing any symptoms but they all end up having issues as they get older (I know somebody who adopted a macaw that came from a smoking household and the poor thing has to spend 3 one hour sessions daily in a box with oxygen for the rest of her life). Me, I am not a risk-taker and one of the 'better safe than sorry' crowd and I plan on been one for the rest of my life.





