Albino birds- that’s the secret. When we look at pigmented birds, the patterns and values that we see are the made by both pigment patterns and shadow. If you take away part of that equation you will learn a lot about how shadows fall on the bodies of birds. Try a Google image search such as albino bird or albino sparrow and you will come up with thousands of results. Look carefully at the ways that shadows fall across the bodies of the birds in these photographs. The shadows do not just fade from dark to light but have shapes and clear boundaries. Sudden changes in light or shade often indicate a change in the angle of the planes that cover the body of the bird.
Many bird photographers prefer to shoot on cloudy days. Overcast skies provide lighting that deemphasizes the shadows and the filtered light gives more of a general illumination. Many of the photographs you will find show this kind of lighting. What shadow patterns do you see on photographs taken under these conditions? I was surprised to see a shadow along the side of the head above the auriculars (ear patch) on many birds. I had never noticed this before studying albino birds. I also noticed a heavy shadow on the lower belly and flanks where the body curves away from the wing. This shadow helps describe the curvature of the body. In many photos there is also a shadow between the primary and secondary feathers where the edges of the secondaries pile up.
You will find a smaller number of photographs taken on bright sunny days. These photos will show crisp shadows that are deeper in value than you see on overcast days. By analyzing photos from sunny days you will get an idea of how to depict birds under these lighting conditions. Once again, look for that shadow above the auriculars, on the flanks and undertail coverts, and edge of the secondaries. You may see shadows at the edge of the scapular feathers above the wing. Also look for crisp cast shadows on the bird’s perch, below the wing, or below the bill.
Copy a few of these photographs to train yourself to understand how shadows wrap around the body of a bird. Now look back at pigmented birds. What have you learned? How will this change the way you draw shadows?