Birds recover from loss very quickly. Not like us at all. Don't try to think of them in human terms, because they live in a very different world. I know it can be fun to compare their antics to ours. But they have very different challenges.
It is very possible that one or both are new. If a mate is lost, they must quickly find another, especially during nesting season. And sometimes, they compete for a mate and chase off the loser. A new male will not likely care for the young of another male, and same for a new female, from what I have heard.
Since your Mrs. knows about the mealworm feeder, it does sound like she might be the same bird, and the male seems different to you. Eventually, and probably very quickly, he will learn from her, and you might hardly notice the difference.
Birds have been around for millions of years. They do not depend on us, even though we sometimes provide them some food, shelter, etc. We do the best we can to help them overcome some of their challenges (many of which are caused by humans) and they don't even know how much they reward us. Keep learning to help them the best you can, and enjoy the show. We are so fortunate! Most people don't even have the privilege of hosting bluebirds.
BlueBars

I agree with most of what you have said bluebars except for one thing "They do not depend on us, even though we sometimes provide them some food, shelter, etc." The eastern Purple Martin is completely dependant upon humans for their nesting sites. If humans stopped putting up housing for them they would have a very hard time ahead. Maybe even dieout. I do not know if there are any other bird species which could be added to the 'depend on humans list' with the Martin but there probably is one or two others.

Wow this sounds so much like what went on here. I put a bowl full of mealies out the day they fledge but none after that for awhile. I find they don't come for them much until the babies are ready to come with them. If this is your same female that means Dad was left to raise 5 kids and it may take a little longer with just one parent. My Pop showed up with the kids later than normal. He's always been nearly 2 weeks to the day and this time it was closer to 3. I have learned that NO, Blues do not always mate for life. There is no question this is Hussy Mom and that Pop got ditched with the babies. I have been feeling bad for Pop (but I guess more for myself). I hope I have not lost him, I know hes not too far, I hear him but still have not found his new nest. Pop has been here for 3 years that I know of. Something happened to his first female between first and second nesting last year and that's when he took up with Hussy Mom. I never would have know it was a different female untill she quit feeding the babies.(maybe the fisrt female took off on him too)? There was no question this years first nesting was Pop and Hussy Mom. The thing is I could never be certain I had the same pair each year, there was always a little something different about each nesting except for Pop, he's always been in the same branches and been consistant with his behavior. His red goes down much farther in the front also.I really hope that I will have both Hussy Mom & Joe Daddy AND Pop with his new female next year. I am looking at the bright side, I should have twice the Blues and after all more Blues is what this is all about! I hope your Dad shows up with the babies soon and as stated above, mealies have nothing to do with survival especially at this time of year!

renee, I didn't know that the eastern Purple Martin is completely dependant upon humans for their nesting sites. Never had the pleasure of hosting them, though I have a beautiful handcrafted martin house gathering dust. What happens to them when homeowners move away? Where did they nest before they were dependant on us? (Oh, sorry, Not to hijack the post - I'll have to go read up on them.) I bet urbanization has taken a terrible toll on them too.
BlueBars

I didn't know that about the Purple Martin either. My neighbor had a Martin house up for years and last year was the first time he had Martins nesting, they were back again this year too. I love listening to them, love their songs. I have toyed with putting up Martin housing however I don't want to steal his Martins, plus he has the better yard for them, less trees.

Donna

Thanks all for the encouraging words. I know deep in my heart of hearts that these birds can find their own food, but I still feel like I let Mr. Blue and his fledgies down, ya know?

Coincidentally, my neighbor across the street told me that she's been seeing "several" baby Blues at her feeders and baths over the past few weeks, so perhaps Mr. and the fledgies are simply taking a vacation across the street. I sure hope so. Letting go is so hard - and these are wild birds! I am in so much trouble when my little boy goes off to college someday (he's 7 now, though, so that's not too soon, thank goodness!!)

Mulli My blues disappear for almost a month after the babies fledge. I don't put too many mealies out then because they don't come around very much until the fledglings are close to feeding themselves and very good at flying. I'm sure that your papa blue will bring the fledglings back to your yard soon. I know I always feel that I won't see the fledglings again and soon after that they show up.

millipuff, where are you located?

Bluebars - I'm in southern Delaware.

In DE, you might have them stay the winter with you. They do stay the winter here in central Maryland. Usually just the parents and the last brood. Until the weather turns warm and they are chased off to find their own matess and territory. Check the CBC count map on the link below.
Bluebars

Here is a link that might be useful: http://www.mbr-pwrc.usgs.gov/id/framlst/i7660id.html

Bluebars - I was wondering if they might stick around. If they do, I'll have to by stock in Grubco... It would be so cool to host them year-round. Do your use the nest box to roost in the winter?

millipuff, we have a Gilbertson PVC nestbox, and I don't think they use it for roosting in winter, but they do defend it and their territory from competitors. More likely they would find a tree cavity (lots of forest nearby).
We offer them mealworms and sunflower chips, and when I have time to make it, suet mix. There is another post called "Great Links and Resources 2008" that has suet mix recipes. I've bumped that post to the top for you.
The most important thing in winter is unfrozen water during extreme weather.
BlueBars