Birch is probably the easiest tree to identify in the entire world
.
The bark is startlingly white with black, horizontal lines all over it.
Best time to harvest is right now in Spring, whilst the sap is still running up and down the trunk. It should peel right off.
During Fall, when the sap starts moving down into the roots for Winter it becomes very difficult if not impossible
to get a good piece off. If you pull off a piece that is less than a third of the circumference of the trunk, the tree has a pretty good chance of survival.
Done at the correct time of year it's so easy one can use a small (sharp) pocket knife.
Good luck!