Wild Mallards are concidered as a Migratory Bird and you must have a Federal Wildlife License called a (Migratory Bird Permit) issured by the Department Of The Interior - U. S. Fish And Wildlife Service in some cases. Under the Code Of Federal Regulations (50 CFR 21) if you obtain your mallard duck from the wail and not from a hatchery or private owner who has a permit to breed them in captivity.

CFR 21.13 "Permit exceptions for captive-reared mallard ducks" reads as follows --- "Captive -reared and properly marked mallard ducks, alive or dead, or their eggs may be acquired, possessed, sold, traded, donated, transported, and disposed of by any person without a permit, subject to the following conditions, restrictions, and requirements." "(a) Nothing in this section shall be construed to permit the taking of Live Mallard Ducks or their eggs from the wild" "(b) All Mallard ducks possessed in captivity, without a permit, shall have been physically marked by at least one of the following methods prior to 6 weeks of age and all such ducks hatched, reared, and reatined in captivity thereafter shall be marked prior to reaching 6 weeks of age." (1) Removal of the hind toe from the right foot. (2) Pinioning of a wing: Provided, That this method shall be the removal of the metacarpal bones of one wing or a portion of the metacarpal bones which renders the bird permanently incapable of flight. (3) Banding of one metatarsus with a seamless metal band. (4) Tattooing of a readily discernible number or letter or combination thereof on the web of one foot. (c) When so marked, such live birds may be disposed of to, or acquired from, any person and possessed and transferred in any number at any time or place: Provided, That all such birds shall be physically marked prior to sale or disposal regardless of whether or not they have attained 6 weeks of age.....

What this means pretty much is as long as you get the bird from a private owner or from a licensed hatchery, you don't have to worry about a federal permit. BUT you can't go out in the woods and find a baby duck or eggs and take them with you. Also there may be a state or local law or permit needed to have them. To be on the safe side If you want mallards outside of ordering them from a hatchery, or getting them from a friend who owns them, Get in contact with your local or nearest office of the U. S. Fish and Wildlife Service and explain to them what you want to do and ask what you need. ALSO check with your State Wildlife Service to make sure about any state or local laws there may be.