[QUOTE=Keeve]
Only if she succeeds in finding a mate.
[/QUOTE]
Well, they advertise pretty well by various means, and men being men regardless of species … 
It might be pointed out that in primitive societies most women are not going to “waste” all that many unfertilized eggs. Most fertlle women with a regular partner will get pregnant within a year. Pregnancy will take up nine months; then breastfeeding the infant may suppress ovulation for up to two years after that. Assuming a fertile span of about 30 years, there thus may be only about 10 time periods within that when a woman is ovulating regularly. In societies where women are almost continuously either pregnant or breastfeeding, probably fewer than 100 ova will go unfertilized.
[QUOTE=Speaker for the Dead]
some birds lay unfertilised eggs.
Since this happens, there must be a reason. Why?
[/QUOTE]
Infertile eggs from infertile fowl.
Some women are just naturally infertile for the same reason. The just are infertile.
S. A. Answer: No Roosters? 
[QUOTE=spingears]
Infertile eggs from infertile fowl.
[/quote]
Sometimes, perhaps, but fertile birds will also sometimes lay infertile eggs. This is not a general explanation.
The same reason as what?
The proximate cause of infertile eggs in laying hens, but not the reason they are so prone to lay unfertilized eggs.