Goose eggs ferility ? some firtile some not collected same week

[Matthew0085]

i have one female goose and I collect eggs dailey im lost on how some eggs are fertile and some arnt its almost like 50/50 or worse ! any input will help thanks

 

[BullChick]

I’ve been trying to figure that out with my ducks for years! I just assume it’s that he finally got his spring swimmers. He mates regularly, but isn't potent right away.