Oh man, sorry to hear about these losses.

I've always heard about the blue bird sky too. I was told that it's because there's no clouds to break up the sun. What that has to do with anything, I don't know.........just what I was told once. I've found it to be true for the most part. Bad day to fly birds. If you think the liberator is going to say that the sky is too blue so they shouldn't release the birds..............well, think again. LOL
As far as why some can make it home and others can't........that's just the odds. There will always be a few that can make it through anything. Don't know why that is either. Don't know how you can figure out who will and who won't. Thing is, the weather man can predict sun, rain, snow, clouds........but they don't predict a day with NO clouds..........so those kind of days basically just are what they are and by the time we know it, it's too late.
I hope the majority of the birds come in. I believe they will.