There are two studies here which are related through the production of stress hormones. The first is a study about the West Nile virus and how sparrows that are exposed to artificial light at night take longer to get better and carry heavier loads of the disease. And this all ties up with the need to maintain a strict solar schedule for our birds because not doing it results in larger levels of stress hormones and a depressed immune system.
https://www.sciencedaily.com/releases/2 ... 111123.htm
The second is a study about how captivity increases levels of stress hormones in wild birds (which is what we have: wild birds kept in captivity).
https://www.sciencedaily.com/releases/2 ... 173547.htm