I used to work in a hatchery and on a farm which produced fertile eggs all yr round. by the sounds of it your drake is doing the job altho with 2 to 1 you may want to make sure they arent stressing her because this can affect fertility. i think the thing about winter is to do with short days birds tend to lay when the days get longer, hence come into season. So on the farm i worked at obviously they used artificial lighting and special feed containg uvb. your fertility rates can vary at any time. our rates depended on the age of birds, age of eggs and breeds, but dont b dishearted by just 1 infertile egg. i used to go thro some trollies of eggs (granted we're talking thousands of eggs) but i'd take of 5-600 bad eggs and count average of 15 infertile on 3 trays of 120. so all u have to do is pick the wrong egg. also b4 putting the eggs in the incubator are u warming them to room temp. and best fertility is in eggs under 2 wks over 2 wks and you half your fertility rate. hope this helps a bit.