To watch a female nuthatch preparing a nest hole is amazing.  She selects an old hole, often an old woodpecker nest hole as in this case and she transforms it.  She infills crevices and/or reduces the size of the cavity using mud and bits of rotten wood.  She will also use mud to reduce the size of the entrance to minimise the risk of predation.  The male, distinguished by chestnut red flanks, keeps guard during this process and will fend off any intruders.  Updale Natural History Recorder