For creating the "Hair Density Texture" for Piero's second "Body Feather Layer", select the original "Hair Density Texture" (the version with a white backhead) in the "Texture Slot Panel" and save the image "as copy" in the "Image Editor" so that it's not linked with the current "Texture Slot Name". Now, load this image in the "Texture Slot Panel" ("Sinlge Image") and rename the "Texture Slot" since Blender copies per default the "Image File Name" to the "Texture Slot Name Field" if the image file is loaded into Blender for the first time. I simply remove the ending which indicates the file type in order to show that it's the name of a "Texture Slot" and not of the image file itself.