The buds open from sugars stored at the base of the leaf. So even a cutting - with no roots - will open its leaves. That said, you might as well assume that your tree is re-rooting. I would start to fertilize lightly, at a quarter strength. I don't know much about paper birch, but I do have a couple birches in my yard - and I've collected their seedlings.

Josh

Thanks for the reply i hope that it is rooting the tree will make an exellent bonsai. if it rerooting, how long should i to repot the tree. id like to get it in a pot four inches in depth.

I understand the allure of the Birch and, when I was in the states tried a few as Bonsai. Then realized there was a reason why you never see one as Bonsai. Sorry but true, they just don't cut it.
Leaf size is almost impossible to reduce so, on a smaller sized tree it looks strange. They, like wild cherry, are just one big pest magnet, every pest and desiese loves to attack them and will. Of course you can always begin again because even the tree dies it will put out suckers.
Sorry to bust your bubble, you may have it a few years but that's about it.

Bob

Shepard, I'd let it re-root all this season, and then I'd re-pot when the tree is quiescent - late Winter, perhaps a couple weeks prior to the date it was collected. Once it has a good mass of roots, then prep it for the show-pot.

Josh