Here`s how we did it on a "primitive man" course a few years ago...
1.) An optional method to drilling into a fully grown, mature tree (and faster?) is to select a birch sapling about 2-3 meters tall (diameter 3-5 cms?)...and to bend the top down towards the ground.
2.) Slice off the tip of the sapling, and insert it into e.g. an empty 1.5 l empty (coke) bottle...
3.) tie the bottle to the sapling and peg it into the ground...
4.) If you`ve done this correctly, the bottle should fill in a couple of hours/overnight.
The idea is, that the "beheaded" sapling will simply grow a new tip, an you won`t be (possibly) damaging a mature birch...
Marko