Chances of eggs being fertile?

[Unruffled]

I have 3 male American Buff Geese and 1 female American Buff. All of my birds( I have chickens and ducks too) free range during the day. My question is this, if I have never witnessed any of the geese mating ( they were all 4 hatched in April of 2020), what do you think the likelihood is of her eggs being fertile?

I mean are they usually very private about it, or do you think I would have probably seen something?

 

[nuthatched]

Have you opened an egg to check?