Mallard ducklings hatch in clutches that average around eight to 10 ducklings. Knowing the sex of the ducklings is important if you want to give ducklings away. If a male, or drake, and a female duckling are paired together from the same clutch, they might inbreed with negative effects. Also, a female mallard, or hen, paired with too many males can be overwhelmed and damaged when the mallards reach sexual maturity. The only way to tell the sex of a newborn baby mallard duck, a concept known as sexing, is anatomically. However, when the baby mallards reach the age of two to three months, additional ways to determine the sex develop.
Examine the duckling's vent. Venting consists of examining the mallard's genitalia for a direct answer about the sex. It is dangerous for the duckling if you do it incorrectly, so try it only if you have experience. Otherwise, take the duckling to a vet or someone who has the know-how. The process involves holding the duckling upside down in your hand to view the vent on its underside before carefully feeling around the edges of the vent for the genitals. Female ducklings have cone-shaped genitals, while the male duckling's genitals are more distended.
Listen to the sounds the duckling makes. The voices of baby ducklings take a couple of months to fully develop, but once they do, they provide a clue to the sex of the duckling. Female mallard ducklings are louder than males, and the females actually quack. Young male mallards make only soft sounds.
Examine the duckling's feathers. Male mallards have green feathers on their heads that begin to show when they are a few months old. Female mallard ducklings have only brown feathers. Also, most male mallards feature a drake feather, which is a curled feather on the tail.
Compare the size of the ducklings. Male mallards are noticeably larger than female mallards. However, this size difference, like the other indicators, takes time to develop and is not noticeable right away.