Any of three species (family Rynchopidae) of waterbirds having a red bladelike bill, with the lower mandible longer than the upper. Skimmers live chiefly in estuaries and along wide rivers in warm regions. At twilight, they skim calm, shallow water with the open bill tip submerged; when a fish or crustacean is hit, the upper mandible snaps down. Skimmers are dark above with white underparts, face, and forehead, red legs, and black wings. The American black skimmer (Rynchops nigra) grows to 20 in. (50 cm) long.
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The three species are the only birds with a lower mandible longer than the upper. They feed by flying low over the water surface with the lower mandible skimming the water for small fish. They are the only birds known to have slit-shaped pupils.
They are tropical and subtropical species which lay 3-6 eggs on sandy beaches. The female incubates the eggs. Because of the species' restricted nesting habitat the three species are vulnerable to disturbance at their nesting sites. One species, the Indian Skimmer, is considered vulnerable by the IUCN due to this as well as destruction and degradation of the lakes and rivers it uses for feeding.
See Sibley-Ahlquist taxonomy for an alternative classification. The genus name Rynchops is often spelled Rhynchops (as in some of the later editions of the works of Linnaeus), though the first version is taxonomically valid, being Linnaeus's original spelling.