(Onychoprion fuscatus)
Hawaiian Name: ʻEwaʻewa
The most widespread and abundant tropical seabird, the Sooty Tern is found in all of the worlds tropical oceans, with populations numbering into the millions. In Hawaiʻi it breeds on all of the Northwestern Hawaiian Islands, with the total population numbering about 1.2 million pairs, making it the most abundant Hawaiian seabird. An additional 100,000-150,000 pairs breed in the Southeastern Hawaiian Islands at Kaʻula Rock off Niʻihau, and Mokuʻmanu Islet and Manana Islet off Oʻahu. The Sooty Tern is found year round in Hawaiian waters, but numbers are greatly diminished from November through January when most individuals migrate to the southwestern Pacific Ocean. Unlike the two noddy species, Sooty Terns are truly pelagic, often found far from land during the non-breeding season.
Although the Sooty Tern does not breed on Kauaʻi, it is often seen from boats around the island, either single birds or in small flocks often associating with schools of tuna. Sooty Terns can be seen from shore, but only rarely, and usually with the aid of a telescope. They are much easier to see in eastern Oʻahu during the breeding season when they are found in huge numbers at the colonies on Mokuʻmanu and Manana Islets.
The black dorsal surface and white under side are distinctly different from the two noddy species, the only other commonly occurring tern species in Kauaʻi. The long forked tail and white mark over the eye also serve to distinguish it. The largely dark brown juvenile Sooty Terns can be distinguished from noddies by their lighter build, white underwings, and indistinct white scaling on the back. The similar Gray-backed Tern is rare in Kauaʻi, but is found more regularly on Oʻahu and the Northwestern Hawaiian Islands. It can be readily separated by its contrasting light gray back rather than the black back of a Sooty Tern.
Kauaʻi Endangered Seabird Recovery Project 