Rynchops

Description

The three species are the only birds with distinctive uneven bills, where the lower mandible is conspicuously longer than the upper. This remarkable adaptation allows them to fish in a unique way, flying low and fast over lakes, streams, and lagoons. Their lower mandible skims or slices over the water's surface, ready to snap shut any small fish unable to dart clear. The skimmers are now included within the gull and tern family Laridae, where they are positioned as a sister group of the terns and noddies. Skimmers also have an additional adaptation in being the only genus of birds known to have vertical slit-shaped pupils. The forehead, ends of the secondaries, tail feathers and under parts are white, the rest of the plumage is black and the basal half of the bill is crimson. Their bills fall within their field of binocular vision, which enables them to carefully position their bill and capture prey. They are agile in flight and gather in large flocks along rivers and coastal sand banks.

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 endangered by the IUCN due to this as well as destruction and degradation of the lakes and rivers it uses for feeding.