Do you know that birds can see a much wider spectrum of colors under the sun than us?
We are scared of ultra-violet rays (UV) (ok, at least most of us ladies…). But to birds, UV is very important.
Importance of sunshine:
Help the production of vitamin D to facilitate growth of bone, beak, and feathers.
Strengthen the immune system (and recent researches discovered that direct sunlight kills PDD virus on surfaces).
Kill germs on skin and feathers.
Reduce the occurrence of cancer.
Enhance happiness. Reduce the occurrence of psychological problems (especially for parrots).
Enhance vision.
Sunshine is not only important for health. Birds will be able to see clearly the appearance of another bird under the sun, and stimulate courtship behavior!
Natural sunlight can only be reached outside.
Unless your bird cage is long-set on the window sill, setting your bird’s cage by the window occasionally may not be enough for the birds, as some glass blocks out 30-90% of the sun’s UV rays.（Source: http://www.birdtricks.com/blog/the-importance-of-natural-sunlight-for-your-parrot/）