Sooty Tern (Onychoprion fuscatus)
Sooty Terns at a nesting colony on the Seychelles (Photo by Andre F. Raine)
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 Hawaii 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 Ka'ula Rock off Ni'ihau, and Moku'manu Islet and Manana Islet off O'ahu. 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.
A portion of a Sooty Tern colony on the Seychelles (Photo by Andre F. Raine)
Although Sooty Tern does not breed on Kaua'i, 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 O'ahu during the breeding season when they are found in huge numbers at the colonies on Moku'manu 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 Kaua'i. 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 Kaua'i, but found more regularly on O'ahu and the Northwestern Hawaiian Islands, can be readily separated by its contrastingly light gray back rather than the black back of a Sooty Tern.