Do Mallard Ducks lay their eggs at one time?

Yes, my wood ducks (male and female) are all almost 4 years old. Only one female lays eggs at my house though. She has laid 3 batches of eggs this year. Her last batch laid and hatched were in the fall. All batches had at least 10-16 eggs each batch. This may be because I always have a pile of rolled corn out for all of the ducks to eat, and a spot that she likes to lay her eggs. Also, I raised my ducks from babies, so they might be healthier than most wild ducks. Hope this helped!

Tip - If you are raising them, make sure you feed them un-medicated food. Give the mom some rolled corn, or any other variety of duck food.