Now that we have a good sense of the shape of the Owl we can begin shading. As you work on each section of the drawing, erase the guidelines so that they are very faint and then begin to shade the area. Make sure you do not erase all the guidelines at once, but only in the area you are working on - the guidelines in the surrounding area will help you visualise the shape of the Owl.
Use tissues or q-tips to help smooth your shading.