You've been spotted

A good gardening day.  Even after two and a half years we are finding overgrown areas, which we had assumed were wild parts of the wood, that obviously used to be part of the garden.  A keen plantsman must have lived here once upon a time.  We chopped down some hawthorn to reveal the birch in the extra.  I had assumed that they were silver birch but now that I can see the trunks I am not so sure.  The bark is a rusty colour where it is peeling off.