I've heard that even if you bulk them up with calcium, egg food, and other supplements this causes the female canary to live a much shorter life than a male. As in, living to be only about 5 or 6, while a male might live to be 10 or in rare cases 15.
But, it's been really obvious and depressing to watch them the last couple of weeks in particular. They're tearing apart preening toys, newspaper and cocking their heads looking for a place to nest. Jerome is singing, they're mating, etc. etc. So I gave up yesterday and put a nest out for them, which they proceeded to start lining with material.
I guess if Rosette does live a shorter life because if it, at least she was able to fulfill some of her instincts.