Pomarine

See, you have a couple of them lying on the water, wounded : you pick them up, and find them both pomarines, the one an old bird, with the two central tail-feathers elongated and rounded at their tips; the other a young bird[…]

[…] to have been pomarines : the first flock of ten or twelve birds were undoubtedly of that species, their great size and clumsy-looking tails clearly pointing them out as such, and all exhibiting white underneath, and long tails[…]

All three species occur in two color phases: a light phase, with dark gray-brown back and white underparts, across which (in pomarines and parasitics) there is usually a grayish breast-band; and a dark phase[…]