never had any probs with fertility at all,maybe one dud which was misshapen if I remember?67 good ones from 3 batchs,lucky i had helpers that took one clutch each leaving me with only one lot which was quite demanding,good luck with them.I found a big net dragged through long grass yielded alot of small bugs etc that were good to get them going,apparently alot of small items is good to get their systems working rather than a few bigger things?