I've never been able to understand how keeping a bird in 'darkness' helps with unwanted sexual behaviour.

I've had a budgie, cockatiel, parrotlet and now a green cheek to enliven my life. I've never covered any of them when they "go to sleep" and I only noticed unwanted sexual behaviours in the budgie.

My budgie (or budgerigar if you prefer) was the first parrot I'd ever dealt with and, with my then "lack of knowledge," I went with the pet store...