by Pajarita » Fri Dec 01, 2017 1:17 pm
Natural light exposure is actually critical to it because the bird needs the different light that happens at dawn and dusk in order to turn on and off their internal clock - this is what regulates their circadian cycles which, in turn, regulate their circannual cycle. Circadian is one day cycle and there are natural biorhythms that happen within it: vocalizations at dawn, foraging, interacting, etc. Circannual is the one that tells them when they are supposed to start courtship, nesting, breeding, molt, migrate, etc.
The mechanics are: at dawn, the internal 'stop watch' starts and, at dusk, it stops and the number of hours in between these two events is what tells their bodies what season it is. Each species has what is called a point of photorefractoriness which actually means the exact number of hours in a day that would start or stop the production of sexual hormones, which would be the ideal number of hours to breed, etc. This number is specific to each species as evolution already determined which time of the year is the ideal one for that species to reproduce and so you have birds that breed at shorter days and some that breed at longer days because, although one would think that all birds should reproduce when the days are long [summer], nature also takes into consideration food availability and weather so, for example, IRNs don't breed when the days are long because that's when the monsoon happens and, if they did, the nest would be destroyed by the strong winds and the babies killed, plus they would not be able to fly about and collect enough food for the babies to thrive. We know the exact points for a few avian species -like canaries, for example, which start producing sexual hormones at 12 hours of light but breed best at 13.5 to 14 hours but would go into molt at 15 hours of light. But we don't know any exact points with parrots although we do know which are short and which are long day breeders -the short day breeders being the most difficult to keep in captivity because they go into breeding twice a year instead of just once.
The thing with birds is that they don't produce sexual hormones all the time and, when they don't, their gonads [sexual organs] are tiny and dormant but, as soon as they hit their own point of refractoriness, they start producing them, their gonads start growing and their bodies start getting ready for breeding. When we keep a bird in breeding condition all year long, year after year, their gonads get huge which causes physical discomfort and even pain as they displace internal organs. And, of course, they are terribly sexually frustrated... that's what makes them regurgitate to their humans, masturbate on them, pluck and even self-mutilate or become chronic layers or aggressive.