I'd like to believe that I can tell them apart, but the truth is I'm guessing. I can usually guess that the two or three crows that linger outside my house and caw when they see me are the mated pair and their fledgling, and that the other crows who come flying are the neighboring families. But in truth, I am only guessing based on behavior. None of the crows I see have any distinguishing marks (variations in size, distinguished beaks or feathers, or other marks) that would help me. When a large (10+) crowd shows up, there is one crow that has a unique voice that sounds almost human. I can hear that crow's uniqueness, but I couldn't pick that strange-voiced crow out in a lineup!