Question

A male cardinal’s red color is an example of a trait affected by natural selection. The females of the species choose mates based on the vibrant colors of the males’ feathers. If females begin using different criteria than feather color when they choose mates, what would most likely happen to the color of the male cardinals over time?
increased variation in the shades of red because there is no advantage in one specific color
increased variation in the shades of red because the cardinals try different ways to impress the females

Answer 1

The first option is most likely: increased variation in the shades of red because there is no advantage in one specific color.

Explanation: Female preference for bright red is a form of sexual selection that maintains and favors a particular coloration. If females stop using color as a mating criterion, that selective pressure is removed, so alleles for different shades are no longer strongly favored or disfavored. Over generations this relaxed selection (plus mutation and genetic drift) will lead to greater variation in male color. The idea that cardinals "try different ways" is anthropomorphic — individuals don't try traits; changes happen by differential survival/reproduction of genetic variants.