[billysmommy]

I seem to remember that at 16, birthdays were a pretty big deal......I think it's just the age. It could also be that she assumes you will be saving the letters for him to read later and then he will know when her birthday is and/or when the letter was written.
I did send my kids first mom a gift for her first birthday after placement because it was only a month after our son was born and I wanted her to know we were thinking of her. Now, we usually just send a card from us and one from the kids, and I have them call her. If I haven't sent pictures in a while, I will send a framed picture or something along those lines.