My drawing relates to Leonardo's studies and notes on the flight of birds, and Tony Silvestri's interpretation, where Leonardo buys pigeons from the market, and releases them so that he can study and sketch the movement of their wings. It's difficult for us to imagine what a problem that would be for a pre-photography era. We can slow down and study film of birds' flight, but Leonardo had to observe and record in real time.
I have to get all the illustrations ready, and the text, before sending to the plate maker, otherwise it becomes very expensive, so I have to be patient. This drawing may have a gilded sun, as per previous experiments. I'm awaiting arrival of the new size from France, to replace the one that got frozen in January and was unusable, and will post the results of experiments with that as and when.