A Peacock's Tail

Description: The tail of the male peacock is a great example of sexual selection. Female peafowl are attracted to male peacocks with the largest and most ornate train. The ability of male peacocks to create a large train is related to their overall fitness. Therefore females are more likely to have healthy chicks if they mate with a male with the largest train. Scientists were able to measure female choice by trimming the trains of normally healthy male peacocks which led to them not being selected as potential mates.

Web Resources:  A Peacock’s Tail - The Guardian, Evolution and Sexual Selection in Peafowl - Wikipedia