Why do male birds have bright colors while female birds have drab colors?

It appears to largely be a result of ual selection. The females of some species like their chaps to dress brightly and dangerously. It's a wonderful way of advertizing to interested predators: 'Hi, here I am and I'm tasty!' Should he be able to survive despite the apparently suicidal tendencies, then it's also a great way of advertizing to interested females: 'I'm not only fit as a fiddle. I look great too. Choose me to fertilize your eggs and you won't be disappointed'.