Okay, I have two muscovy hens who mostly live with my chickens (I know, normally not really a good idea, but they sleep in the chicken run at night instead of with the mean geese and other ducks since they joined the flock later.) Some of their eggs have been fertilized by the drakes (not muscovy) and some haven't. Usually it goes in waves, they're fertile for a while, then the next week or two they aren't. I know they get more than their share of attention when they are allowed out to run with the other birds, but wondered, as a general rule, how long they stay fertilized after a mating. I know chickens can shoot off fertile eggs for up to a month. What about ducks? They laid for a while, then stopped for a while, and are starting back up again, but before I take up valuable bator space for a week or more to check them, I wondered how often they have to be allowed to be bred if I want the eggs to have the likelihood of fertility. And yes, I know when you cross breed with muscovies that half the eggs won't develop anyway, even if the drakes are being amorous, and that the offspring probably won't be fertile. But those babies are the cutest danged things I ever hatched!