Pekin ducks are the most popular commercially raised breed of duck in the United States. Both sexes start out as fluffy yellow ducklings and grow into pure white adults. They are also about the same size and weight. But that doesn't mean sexing them is difficult. If you know what to look for, you can easily tell the difference between male and female Pekin ducks.
Listen to the duck's voice. An adult female Pekin duck has a loud and forceful quack while the male's quack is lower and softer. Ducklings start to show voice changes at three weeks of age.
Examine the back of the duck's neck. The males often pull the females' feathers out when grabbing them for mating. The female likely will have missing feathers on its neck.
Look at the duck's tail when the duck's wings are folded. The female's tail feathers are smooth. The male has a curled feather on top called the drake feather.
Ducklings can be sexed by squeezing the genital area and examining the sex organs, but this method can harm the ducklings and is unreliable unless performed by a veterinarian or professional duck sexer.