They can but once the female starts incubating you don't see them very often. You may just be missing them. What you could do is very carefully take a sharpie and mark a small dot on one of the eggs and then check the next day to see if the mark has moved. The eggs are turned during incubation so the dot should not stay in the same place. Even if the dot doesn't move though give the eggs the proper 14+ days to hatch, so count from the day the last egg was laid and then at least 14 days from that date to decide if the eggs aren't viable anymore. I have had a male go missing when the female was incubating, he was gone for four days but she as still there. Good luck, hope you are just missing seeing them.

I would like to invite you to join the bluebird nut cafe forum. It is much more active than this site and we have many veteran bluebirders that can give quick answers. Check us out! http://bluebirdnutcafe.yuku.com/

Judy, I would observe the box for a couple hours at a time and make sure you know if anyone is showing up. Also, you can place an obstruction like a blade of grass in the hole, and if it's gone you may have activity. Make sure the wind can't also remove it. It's hard to say exactly what happened to the mother. Hawks, owls, pesticides, car accidents, etc. All possibilities. Unless you find a body, you might never know. I've had several parents go disappearing and I know the sad feeling and thought about what may have happened. I've lost several female bluebirds, and just this year, my first couple male bluebirds. It's a tough world they endure. If they're truly abandoned, try to find the number of a local wildlife rehabber and give them a call. You should look into this BEFORE an emergency occurs. Its good that you're feeding, but don't force feed them! ~Tim~ Here is a link that might be useful: Bluebird Widows, Widowers and Orphans

I may be way off base here, but I have heard of a bluebird pair building multiple nests, but only using one for their eggs. Is this a possibility? It would concern me that the other nest seems to have been abandoned. You can always candle the eggs to see if their is development inside. I did that with my bluebird eggs last year when they didn't hatch on time.