I thought it may be useful to know these little facts:

Never take a wild baby duck in without knowing for sure that is has not been abandoned. Very often the mother is around but afraid of coming out of hiding. Give it some time before even considering of catching it.

Call your local “Fish and Wildlife” when it comes to wild animals. It may be illegal in your state to possess one without a license. Fish and Wildlife will definitely help you. 

Baby ducks require the right temperature so a heat lamp may be required.

Mallard ducks are cute pets. You better think twice. They are messy and their poo most likely contains salmonella. They have no control over their anal glands and poo anywhere, even while they sleep. They are not pets. Wash your hand after handling them or their equipment.

Ducks are pack animals. They need to socialize with other ducks and you are not a duck substitute.

Ducks will eat bread, but it is not a healthy diet for them. It’s like eating candy instead of meals for you. It will make them sick. Get unmedicated waterfowl feed at the local feed store. You can temporary feed dry cat food or fish pond pellets to them, since they contains the right protein amount.