by Pajarita » Wed May 21, 2014 10:59 am
Photoperiodic means that their life 'periods' (as in seasons like breeding season, molting season, migrating season, resting season, etc) are governed by light (photos in Greek means light). It's the principle on which the avian circadian (about one day) and circannual (about one year) cycles and all biorhythms (life cycles) are based.
What I am going to give to you now is an abbreviated and simplified version of it, it's much more complex than this but I hope this will give you a good understanding of the subject.
The entire bird body and its functions are 'managed' by different hormones secreted by different glands at different times. The 'master' gland (the one that sends the 'signal' to other glands which, in turn, might send a 'signal' to still other glands) is called the pituitary gland which is deep inside the brain (in reality there is a close relationship with the hypothalamus but I am not going to go into that). This gland hormones (the 'signal') are 'turned on and off' by light. The presence or absence of light sets their 'internal clock' (circadian and circannual cycles) so their body knows what is supposed to do and when.
The biggest difference between birds and mammals is that we have photoreceptors (light sensitive cells) in our eyes only, so, if we close our eyes, we register no light - but birds have photoreceptors deep in their brains and their cranial bones are so very thin that light actually goes through them and reaches the photoreceptors in the brain, activating them (this is why just because a bird is asleep, it doesn't mean that his endocrine system is not 'activated' if there is light in the room, even red light which works for mammals but not for birds -I mention this because lots of people say their parrots are fine because although they stay up at night, they take naps during the day but this doesn't do anything for the endocrine system - and also because some people have taken to using red lights with their birds thinking it prevents them from registering it but, although this works for mammals, it doesn't work with birds because red light traverses tissue faster than any other light so their brain photoreceptors are still registering it).
Now, the other big difference about birds endocrine system is that they do not produce sexual hormones all the time or every pre-determined number of days, weeks or months (like mammals do), they only produce them if conditions for breeding are good. If conditions are propitious, the gonads (sexual organs) become active and grow; if conditions are not good, the gonads go dormant and shrink. These 'conditions' are what we call 'breeding triggers' and there are three: light, food and weather. Birds from temperate climates always use photoperiodism (light) so, when the days are long enough (there is a precise number of light hours in the day that would 'set' the clock, this number is slightly different for every species and it's called the point of photorefractoriness - I don't think there are any studies with parrots but, with canaries, we know they start producing sexual hormones when daylight reaches 12 hours, achieve their peak at 13 to 14 and stop at 15 hours when they go into molt), their gonadas become activated and start to grow preparing for breeding. Birds from tropical and subtropical climates use food availability as their first trigger and weather as their second so, when the wet season is over (no more constant rain and/or storms), plants grow and start to bloom and bear fruit and that's when birds breed. Problem is that, in captivity, it's always good weather inside a house and food is always rich and plentiful BUT the good news is that ALL birds, even the ones that live smack on the equator where there is only a 20 minute difference of light hours between the seasons, are photoperiodic and would revert to using light as their primary trigger for their breeding cycle (there are studies on this).
Supposedly, for tropical birds, we could manage their breeding cycles through food availability - if we knew exactly the composition of breeding and resting season food (resting season is the period when they don't breed which we would call winter) in the wild and were willing and able to micromanage it to that extent but I don't think anybody is. I know I am not, I do give them less protein and no sprouts (they are strictly breeding season food) during the winter but that's about it. So we have no choice but to use photoperiodism.
Why is it so important to use photoperiodism with pet birds? Because:
a) if we make all the conditions propitious for breeding all year round (long days, rich and plentiful food and good weather), they would continue to produce sexual hormones, their gonads would become hugely enlarged and the bird ends up not only severely sexually frustrated (imagine been aroused all day long, day after day, week after week, month after month with no relief in sight) which is the main cause of behavioral problems in pet birds (screaming, biting, plucking, self-mutilation) but also in constant physical discomfort if not pain (there are cases of birds that have peed blood because their gonads are so large that they have displaced other internal organs).
b) the endocrine system is not only for breeding. It controls everything else as well: appetite, mood, growth, immune system, sleep, energy level, etc)
Now, there is an added trick to keep a bird photoperiodic and that's exposure to dawn and dusk because it's the change in the actual sun light spectrum that sets this internal clock. If you look at many posts about chronic laying in hens, you will see that a large number of avian vets recommend using Lupron (or some other brand that does the same thing which I personally think it's a hairbreadth short of immoral -I can explain why if you want) on them, while some would recommend lower protein (good idea!) and longer nights. But longer nights and shorter days are not enough, you need to follow the sun. Period. Why? Because we can slowly increase or decrease light intensity (as it happens during dawn and dusk), we can even elevate or lower the angle (as when the sun rises and sets) but we can't change the spectrum because light bulbs always have the same spectrum all the time! There are few studies about this because, most of the studies done on sexual hormones and breeding were done to prove that birds can go into breeding condition with regular short periods of light (there was one that managed to make birds breed on just four hours of light at a time separated with short intervals of darkness) but there is one that I know of that hits the nail right on the head (I can't post the link, my internet explorer goes down when I try but it's called "The influence of light wavelength on reproductive photorefractoriness" so you can look for it). But, even without this particular study, I would still be convinced this is true if for nothing else that I've been doing this for so many years this way and it works like a charm (mind you, it's not that I am genius and figured this out by myself, it was just that I've had canaries all my life and all good canary breeders know you have to keep them attuned to the seasons so, when I started taking in parrots, I just kept on doing the same thing I've done all my life). I've taken in screamers, biters, chronic layers, pluckers and self-mutilators and, although success was not 100% with the pluckers (50/50 I would say - all of them got much, much better but there were some that continue plucking either a small part of their body or only during breeding season), all the screamers, biters, self-mutilators and chronic layers stopped. And that simply cannot be a coincidence!
Hope this clarifies the subject but, if anybody has any questions or doubts, please feel free to ask.
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