Silver Birch Tree Training/Pruning

Actually, I don't recommend tapping birch trees as, unless the holes are sealed tight afterwards (and we thought ours were), they weep, infection gets in and the trees suffer, Our trees never recovered and had to be cut down. Silver birch are short lived trees at best - maybe 30 years so it may not have been the tapping that killed them but I doubt that it helped.
Birch sap wine was nice - a bit resinous, like Greek Retsina, but not worth killing a tree for!