Why are male birds more beautiful?

Scientist Charles Darwin gave many arguments about this issue in his ‘Mate Selection Theory’ (Theory of Sexual Selection). He wants to say that some differences between men and women are created because they are helpful in the evolution of a species. Many biologists believe that the purpose of this difference is to protect the female mate from possible attacks by enemies.
The female bird has to sit in the nest all the time to hatch the chicks from the egg. At this time, he has almost no defense system. Therefore, the color of female birds is usually plain, so as not to be easily noticed by chil-vultures. In contrast, their male counterparts have attractive colors and decorations