I've had one year when none of the eggs my russians laid were fertile. And then other years when half to two-thirds of them would hatch. It seems fertility is best in the first batch laid of the year by each female.

I do recall my females laying a couple eggs out in the open. I don't think they hatched.

I don't know what is influencing the fertility rate. I have one adult male and two females. Next year there will be two adult males. That may improve things.