I always talk to my birds. To other people I probably sound crazy, lol.
I tell them when I'm leaving and when I'll be back, I tell them I'm leaving plenty of food for the day so they'll be fine. If I leave for a longer time I tell them someone is going to come and take care of them and that she's really nice and will take good care of them.
But I also tell them whenever I'm doing anything in their cage, like cleaning, setting up new toys, giving them their bath, filling up food, etc.
I think hearing me talking to them in a calm voice helps reassure them that everything is okay.