A friend wrote to tell me that she had covered the perches of her bird feeders with material to keep birds’ feet from contact with cold metal. She has a kind heart. Actually, birds have adaptations to foot muscles, nerves, and blood supply that make damage from cold weather unlikely. While looking for information on this in Cornell Lab’s “Handbook of Bird Biology,” I learned that some birds have fingerprints. The feet of birds like raptors and parrots have papillae, small, nipple-like projections that cover the bottom of the foot. They form patterns that vary from individual to individual, allowing birds of similar appearance to be identified one from another. This is said to be handy in particular for identifying birds of significant value, birds stolen for instance. I wonder if you can scan bird eyes for the same pupil differences used to identify humans. Probably. Generally speaking, at this point in human development we can do way more than we need to do.