The black skimmer (Rynchops niger) is a tern-like seabird, one of three very similar birds species in the skimmer family found in South Asia, Africa, and the Americas – Black, African, and Indian. The three species are the only birds with distinctive uneven bills with the lower mandible longer than the upper. This remarkable adaptation allows them to fish in a unique way, flying low and fast over streams. Their lower mandible skims or slices over the water's surface ready to snap shut any small fish unable to dart clear. The black skimmer has an additional adaptation and is the only species of bird known to have slit-shaped pupils. Their bills fall within their field of binocular vision and enable them to carefully position their bill and capture prey. The black skimmer breeds in North and South America.