That is really tough, I know. I've been through it. Some people are very good and corresponding, others are not! I agree, it is important to trust that you picked a good home in the first place. Kind of like children, you have to let go! One of the best things, is to remain positive and open at all times. Some people are just really CRAPPY at keeping up with friends and family- I know, I am one of them.
Until you have raised/restored an animal/fid to good health- you really don't understand how much heart and soul goes into it. There are people who are just happy that their breeder/rescue co-ordinator is THERE when THEY feel they need it! I have had people get back to me only YEARS later to say, HELP! Then, I hear how great they are with the fid, see pictures etc etc etc etc. The other post is correct, it could be guilt. It could also be, just no time/busy bonding/nothing is wrong, nothing thought to report and pride could be there too. I am sure you screened the family well, they might just sort of think in their mind "well, I am doing it all right and everything is fine, why do I need to treat her like my MiL??". I'm not saying I agree with that attitude, just that- even good parrots with great homes- well they don't GET it if they haven't raised/restored those babies!
Just do your very best to remain positive at all times and be there should/if they want or need you. It is very hard to let them leve the next, I know. But, you sometimes just have to have faith and trust that all is well. No news is good news, kind of thing! Some people, I guess are more intuitive or more sensitive or just more "yakity" and fill us in with the details.
I would say- after re-homing several hundred birds- that its only about 1/8 of people that communicate both initially and continuing long term, rain or shine. Its about 1/3 that I hear from quite often over the first few months or so, then it peters off. But, I like that- because it allows us to kind of cement a mutual relationship and I know that- if they ever need something, they will be comfortable to ask me. I realize how difficult it is. Unfortunately, its one of those things that just is. I am sure you did a good job finding good homes, so my advice is to trust your gut and be positive and open with your fids new people always!

J