Fertilized quail eggs question

[Incubator Madness]

My last batch of incubated eggs, only half are fertilized. I have Coturnix; 1 male to 2-3 female. They are 2 years old. My question, would it be the male, even though having foam, may become sterile, or the hen, even though laying daily, could she be sterile? Or both? Is it best to just keep rotating the younger birds and not have any over a certain age?

 

[JacinLarkwell]

Your quail are actually pretty old. They only live to be 2 or 3

 

[Quailobsessed]

I think the males' fertility decreases after about a year.