I have tried for the last 8 days to call for Ned and Nellie with no luck. It really is so odd since they were like clockwork for 10 weeks and now nothing. I did see an owl in our back yard on Wednesday and we shared a couple of hoots. It's really hard to tell who (no pun intended- well just a little) is who unless they are together. When they hoot, the male has no trill at the end of the "Who cooks for you" while the female has that trill.
Jen came out and gave me the antenna and transmitter (Ned has his own frequency) so I will try and find Ned. Nellie is likely sitting on the nest and it is his job to feed her since she has to keep the eggs warm. So if we find Ned, the nest could be nearby.
Another possibility I do NOT want to think about is the Nellie has gone to owl heaven. Most city owls die when they are going after a mouse and a car hits them but the other way they can die is by people putting out rat poison (or even toxic yard chemicals) and mice or voles eating that and then the owls eat the mice. She is banded so I would have hoped that someone would have reported it. If Nellie is gone, then Ned will be looking for a mate so he may not be in the neighborhood around feeding time. It's almost too late now to nest so he may have to wait until next year.