I did this sketch while in high school. My mom and dad draw and kept their pics hidden away in a closet. Mom's artistry came out on pillowcases, and curtains. She would take fabric paint and make ordinary cotton linen look extraordinary. Flowers, vines, and critters sometimes even a bug or two. My Dad drew in his teenage years and while as an Air Force sargeant. He drew a pic of mom when young and himself plus homes he wanted to make. So as a teenager when I showed an interest they bought me Jon Gangy. Still have the book. Other than Professor Emeritus Gary DeClue who over saw a fine arts building and created many programs for school districts no one else has published art I know of. The book like so many things in our family is our visible symbol that we too are artists mostly folk art but capable of so much more. I do have a son that does technical sketches originals that create some of the wonderful products we use today in smart phones.
Mentors for the robin which was sketched after watching many hours out my parents front door bird feeder Jon Gangy, my art teachers in Jr. High, and my mom and dad. Why I did not take art in high school? Simple. You were only allowed one elective and I did music (Dad plays guitar and the whole clan sang like a choir Baptist style) When I became a math teacher all my students where taught math art and geometry drawings which by the way is the basic foundation of art lines, squares, rectangles, spheres.