Determining gender in adult guinea fowl is not easy. The helmet and wattles are the easiest to observe from a distance for differences. Wattles are the two fleshy skin tags that hang down from the bird's face. In adult males, the wattles can cup forward and upward. In adult female guinea fowl, the wattles tend to be flatter.
The helmet is a horn-like structure that sticks out on the top of a guinea's head. In males, the helmet is bigger than in females.
Male adult guinea fowl tend to only make a one-syllable sound that is a "check" noise. Females tend to make a two-syllable call that can sound like they are saying "buckwheat" or "okay".