The Skimmers, Rhynchopidae, are a small family of birds. The family comprises three species found in South Asia, Africa, and the Americas. A unique feature among these birds is the vertical cat-like pupil in the eye surrounded by a dark brown iris. They are the only birds known to have slit-shaped pupils. When fully opened the upper and lower points of the papillary aperture are marked by distinct angles so that even at this time the opening is not circular.