If you listen carefully, the sound he makes while snuggling into a depression in the soil is a very rapid clicking, a bit more subtle than the tidbitting sound. This is the nesting vocal, and he's doing it for himself as much as to entice a hen to come agree with him that he's found a splendid nesting site.
My two roos do this a lot. They especially enjoy jamming themselves into a dark corner of the run, either inside or outside. Sometimes they even get into a nest box and call attention to it as if they only just then discovered the nest and its superior suitability for laying.
