About Rynchops niger Linnaeus, 1758
The black skimmer (Rynchops niger Linnaeus, 1758) is the largest of the three existing skimmer species. It reaches 40–50 cm (16–20 in) in total length, with a wingspan of 107–127 cm (42–50 in). Individuals of this species weigh between 212 and 447 g (7.5 to 15.8 oz); males average around 349 g (12.3 oz), while females are smaller, averaging 254 g (9.0 oz).
The basal half of the bird's bill is red, and the remaining portion is mainly black. Its lower mandible is much longer than the upper. The eye has a dark brown iris and a distinctive catlike vertical pupil, a trait unique among birds. The bird's legs are red, and its call is a barking kak-kak-kak.
Breeding adults have black plumage on the crown, nape, and upper body. Their forehead and underparts are white. The upper wings are black with white along the rear edge, while the tail and rump are dark grey with white edges. Underwing color ranges from white to dusky grey, varying by geographic region. Non-breeding adults have paler, browner upperparts and a white collar on the nape. Immature birds have brown upperparts with white feather tips and fringes; their underparts and forehead are white, and their underwings match the coloring of adult birds.
In terms of behaviour and ecology, black skimmers spend much of their time resting in large groups on sandbars located in the rivers, coasts, and lagoons that they inhabit.
