The eggs may be fertilized. This time of year, however, none of my runner drakes is showing any interest in the girls so any eggs would likely not be fertile. But, my girls also quit laying some weeks ago.
If you aren't interested in hatching out ducklings -- and if your female hasn't been setting on those eggs -- you can always just eat them. Fertilized duck eggs are okay to eat. Just keep gathering her eggs every day so she doesn't have a chance to go broody and make winter babies -- although I don't think that's going to happen.
While I think more ducks is always better, as long as your drake doesn't overbreed your girl -- mine actually bleed from the back of the head from being mounted so often -- you can probably get by with two ducks.