Yes actually I do have an update. Although very much late! Mom helped Pop with taking care of his brood and they never made another attempt. (I would have enjoyed it, but I had my doubts) I was out today and I heard that typical single note bluebird call! They're out there some where! lol I heard a HOSP coming from the direction of a pair of nestboxes...thought I had to bring the Van Ert out...in September! It was actually farther off. In previous years I've had flocks of blues in the fall check out my boxes so now I'll have to be on the lookout!

My best guess would be that the tree swallows built a nest somewhere else and it was taken over. I've seen a bird lay an egg in an empty box once before. Tree Swallows are limited in their time to lay since they are neotropical migrants, and have to get back to South America. I wonder if you could put a fake nest under the egg so the babies have a better chance of survival?

Bluebirds are cavity nesters, so it makes me wonder if it was some other bird.....like an indigo bunting or another bird that might have a little blue in it. I also wonder if it was roosting there at night? Did you ever see it there in the daytime? Maybe it was in the process of constructing the nest? These other possibilities explain it's returning, rather than grieving it's lost eggs/babies. Maybe believing that will help you not feel so bad about it. Did the condo management talk to you ahead of time? I would have real problems with that. :(

My questions: Has anyone used the recipe included in this post, or one similar, and with what results ... ? Is vitamin D necessary or helpful (for birds) with the calcium? (Calcium carbonate powder is available without vitamin D.) Or what do you suggest to help with calcium intake? I learned on sialis.org that mealworms are calcium depleting. Because the female lost her mate, and the new young male appears to need lots more training, I upped the number of mealworms being fed to "our" bluebirds - her, the new male, and the fledglings. She now has 5 more eggs laid. :D Also on sialis.org, there is a recipe shared that might add calcium when feeding mealworms. ... I'll give the link and paste the recipe here. Any input is welcome. (For now, I have chicken egg shells, rinsed, sterilized, and ready to pulverize. I can at least make them as powdery as possible and shake in a bag with mealworms when feeding.) "Another option is to make up the following mixture which wildlife rehabbers use, and coat mealworms with it before offering them to birds (thanks Casey!) - 1 cup high quality kitten kibble. Wal-Mart's Maxximum or Iams is good. - Soak in 1 cup warm water until the water is absorbed and the kibble is no longer crunchy. - Two hard cooked egg whites - no yolk - chopped - Calcium carbonate tablets plus vitamin D that will equal 1800-2000mg. calcium (probably 3 or 4). Crush tablets. - Combine in a blender. Final consistency similar to thin Dijon mustard." http://www.sialis.org/calcium.htm