Birds and Aromas
I am sure that you have heard of the canary in the coal mine stories. These birds were used due to their sensitivity to air pollutants to protect the humans working in these areas. While this use has been phased out with the advent of more advanced technology, the visible signs of distress were easily spotted.
Please note that there has not been many scientific studies done regarding animals and fragrances and a good bit of mis-information is out there on the web. None of these claims have been evaluated by the FDA nor can be backed up by scientific research. Any information contained here is not intended to diagnose, treat, cure or prevent any disease. If your pet appears to have serious health concerns, consult a vet!
When it comes to using fragrances around your birds, it is always best to err on the side of caution and remember the canary in the coal mine story. I wouldn't recommend using any aroma producing item in the same room with them. While I am pretty sure that there are some folks out there that may do this, I cannot advocate it to be a safe thing to do. There are some products being touted as pet safe but many do not account for birds!
I would steer clear of any aromatic - chemicals (Febreeze, Glade etc.), scented candles, diffusers, tarts & perfumes. Birds are sensitive to indoor air pollution, scented candles included. Birds that have experienced fume inhalation can show immediate health issues, such as trembling, wobbly legs. If you see these signs please consult your vet immediately.
If you are looking for air freshening, because let's be honest our pets can produce the "stink", try using an odor eliminating unscented candle. Diffusers should be avoided around birds due to their respiratory tracts being very sensitive, and they may develop more serious problems if you use a diffuser. Beeswax and Soy candles can be a safe alternative. Always make sure that your bird is kept away from any flame. Always keep a close eye on your bird's behavior while these products are in use. If you notice any unusual activity/behavior discontinue use. Be vigilant and keep your friend safe!