Wow, there are a lot of answers her, and I'm not going to read them all to see if I'm repeating anything.
My answer is first: it depends. My Khaki Campbells ( mine are selected for egg production) lay eggs almost every day. My best layers only miss 20 days or less a year. Indian Runners may lay almost as many eggs (or most have the potential). Anconas and most other ducks (not meat ducks) will lay about 4 eggs a week, some lay more.
If you forget to feed them a day, they will not lay a day or two later. If they are getting less than 15 hours of light in their eye per day, they will lay less to none. (I put a 25 watt bulb in with my laying ducks in their coop at night)
So, choose a layer, feed well, clean water daily, give them a light when its late fall and winter, and you'll get the most eggs possible, out of most chicken, duck, and corturnix quail alike.
(not turkeys, geese, or pheasents, and not all chickens)
BTW: Hens lay with or without drakes. Ducks can lay eggs for 7 years or more, but are most productive the first 4. If you put your ducks in an enclousre at night (w/a light to get eggs once they are 6-7 months old, or for the older girls, if they are under age 5 you should still be getting eggs from most ducks) they will lay their eggs in the pre-dawn hours, and you let the ducks out and gather eggs right off the ground. I just put some straw in a corner, and they usually lay there.
If your enclosure is very safe, leave them out. If there is a chance of break in from determined carnivores, lock those ducks up in a dog house, a crate, in a tiny A frame you've built - but lock them up! And, if you want winter eggs from ducks that are still laying, your tiny light will keep eggs from freezing usually.
