Your bird needs sunlight. Windows filter out UV, which birds need. Full-spectrun light is the answer. NO incandescent bulb is full-spectrum, but that's a good thing. The answer is flourescents...and it doesn't have to be expensive. You can go broke buying specialized bird lights, but why? Walk into the closest Home Depot, Menards, or whatever, and look for the displays of CFLs...compact flourescent lights. Find the ones that are labeled "Daylight". In my store they're about $7 each. These will give your bird good light, cost much less tom operate, and last about six times longer...they're so efficient thatAustralia and Canada have made regular incandescent bulbs illegal in the near future.

What about mounting them? This is a track mount on the wall above Sammy Scarlet's cage. The lights aredaylight CFLs, equivalent to three 60 watt blubs, and using 54 watts total. The unit is a do-it-yourself system from Menards that cost $80 and went up in an plugs into an existing outlet and has its own wall switch. It could easily be ceiling mounted also.
Below is one end of the big-bird room on the third floor. The lights in here are CFLs mounted in triple swiveling fixtures that cost $9 each...the space is 850 square feet, and on a cloudy day it looks like this inside.
Here's one of the playstands with lights and hangers shown