Final answer:
An evolutionary arms race between male and female birds can produce sexual dimorphisms, such as differences in body size and colorful plumage.
Step-by-step explanation:
An evolutionary arms race between male and female birds can produce sexual dimorphisms, such as differences in body size and colorful plumage. These traits arise from the variation in reproductive success of the males, who compete with each other to attract females. The more successful males pass on their desirable traits to offspring, creating distinct phenotypic differences between males and females.