Sand Martens burrows

In the sunken lane alongside Hoppins Field.
The lane is cut very deep at the top of the hill shallower at the bottom. Before the road was tarmacked the sandy soil would have washed away every Winter as traffic stirred up the mud.
I wonder how many generations of Martens have bred here, and how tall the 'cliff' had to be before they deemed it a worthy nesting site?
Erosion isn't always a bad thing, something or someone can usually take advantage of the ' niche' created.