In 1984 they imported twelve fertile eggs for further breeding.

Female mosquitoes - males do not bite people - need human blood to develop fertile eggs.

How can a bunch of hens lay fertile eggs without a rooster?

A male can become a female and successfully breed, laying fertile eggs.

I can't see a reason to let good, fertile eggs go to waste.

The youngest pairs to lay fertile eggs were 10 years of age.

They will lay their fertile egg in an isolated pool.

Finally, he gave them a fertile egg that needed care to hatch.

Only the fertile eggs last the winter, with the next generation emerging the following spring.

This kept the ducks healthy, and meant a higher number of fertile eggs.