Sir Thomas More wrote to a female offspring that he'd been nice to her when she was young and had only ever used a birch made of peacock feathers on her bottom so as not to cut it up! I guess he meant he used the long tail feathers and pulled the vanes off leaving the shafts.
There's an old prison which you can visit, think it's in Scotland, it has a birching table complete with a birch nearby, there's several images and a short video clip online of visitors trying it out!
Funny thing is that one of the first discipline images I ever liked was in a comic in 1968 and showed a Tudor lad about to have his hose pulled down to be birched!