Among peacocks the males with brightest and showiest feathers are favored as mates by peahens what is this example of?

This is an example of sexual selection. Sexual selection is the process by which certain heritable traits become more or less common in a population as a result of mate choice. In peacocks, the males with the brightest and showiest feathers are most likely to be chosen as mates by females, and so these traits become more common in the population over time.