I returned to the subject of the Heron to day. I approached this one in two stages. The first photo shows as much as I did at the first sitting - I decided to leave a white space for the Heron rather than working it over the background as I did with the last piece.
I completed the sketch when the first layer of paint and ink was completely dry. I also worked in a little more charcoal and some white chalk highlights when the second layer of paint was dry.
There is always the danger of overworking a piece that requires careful detail as with the heron in this case, but I am reasonably happy that I haven't done that here.