From The Owl Research institute

Have you ever noticed how much variation there is in the faces of Northern Saw-whet Owls? Take alook at these side-by-side comparisons and see how different each owl can look from the rest.

One datapoint ORI collects from each owl is the amount of facial white right around the face. As you can see, some owls have a lot of white, and some have hardly any at all; it certainly is interesting to see all the faces that pass through our station.