Animal Reproduction (a booty call for the species)

Birds: what sexy bottle caps you have

A book, _Sperm Wars_, asserts that sperm competition happens in humans.

You should have included mating rituals in high school settings. Humans are the only species that engage in recreational sex as the norm.

During your discussion of the first bird you mentioned that the male contributed "a few millimeters of sperm". Did you mean milliliters?