I agree with Brandy (big surprise
) Birthfamilies are not mind readers and communication is key. Also know this, even in the best OA most birthparents are walking on eggshells... afraid that they are going to say something that will get them cut off. It's not rational, but there it is. I still have that iggling fear today. And my son is 25 years old and on his own!
Additionally there is the really intense feelings that contact brings, especially when the kids are little.
One more thing. I would reframe the gratitude to birthfamily stance to one of child centeredness. Most birthparents are not aware that they are actually important in the life of the child... after all they were "replaced" by you. (I have heard many times "Why should you be involved? He already has a Mom, he doesn't need you. Two will only confuse him.") You need to be the other voice that says, "Even though you are not parenting you are vital and important in the life of this child."