Eggs not hatching, Hawks?

[ron20m]

I have several more than usual of nests with eggs that are not hatching, and probably wont. It seems like I'm having fewer hawk attacks than usual.
Usually I see some evidence like feathers on ground etc and have seen very little. I am working a 1/2 time job and even spending more time at home than I have for last 25 years and still haven't seen many.
I have over 50 pairs and my theory is the bigger colony can alert and protect better.
It always seems worse the first few arrivals and when I down to the late 2 or 3 nests to fledge.
I've witness a pair of hawks come in about every 30-45 minutes one year until I couldn't take it anymore.

Are there a lot of other reasons beside predation that causes nests of eggs to be abandoned?

[TheSmiths]

Eggs are sometimes infertile though the pair will often attempt to renest if that is the case and it is still early in the season. Females can also be lost to illness and accidents. Only the female has a brood patch for properly incubating eggs so without her the eggs will not hatch.

[ron20m]

Last night I puled out six unhatched eggs with complete embryos in each. Mom must have been killed by a hawk a day or tow before hatching. Rare for me.
I've had eggs left or not hatch but not a whole batch nearly ready and not hatch.

[Spiderman]

If a hawk or owl gets the female at that stage the party is over the male just moves on.

If the young hatch and will fledge in 10 days or so the male will continue feeding and caring for the young.