Good evolutionary reasons for that, of course -- it's the males who are rendering themselves far more vulnerable by discarding their camouflage in favour of eye-catching plumage.
(Which is odd, given that in most species of garden bird, at least, *both* parents provide food for the young. It's not as if the males are dispensable, like spiders, the moment they have fertilised the females; if the male bird gets taken by a predator due to his flashier colouring then the chances of survival for the offspring presumably plummet!)