a yellowish orange (can also contain some red) bill tipped with black (males) as opposed to the black/orange bill in females.
During the final period of maturity leading up to adulthood (6–10 months of age), the plumage of female juveniles remains the same while the plumage of male juveniles slowly changes to its recognizable colors. This plumage change also applies to adult Mallard males when they transition in and out of their non-breeding plumage at the beginning and the end of the summer moulting period. The adulthood age for Mallards is 14 months and the average life expectancy is 20 years