Birds of Singapore
by the Bird Society of Singapore
Onychoprion aleuticus
Family: Skimmers, Noddies, Terns, and Gulls · Status: Uncommon migrant · Size: 32–34 cm · Conservation: Vulnerable
Breeds along the coasts of Siberia and Alaska, wintering in coastal waters of southern China, Hong Kong, the Philippines, the Malay Peninsula, Singapore and Indonesia.
A medium-sized tern, the breeding adult has white forehead contrasting with black cap and lores, grey upperparts and underparts, white rump, and long deeply forked tail; all-black bill and legs. Underwing shows a diagnostic dark trailing edge on the secondaries resembling a bar, visible in all plumages. Non-breeding adult has mostly white crown with blackish ear-coverts and nape; underparts white. Juvenile has dark brown subterminal markings on upperparts and a reddish base to the lower mandible. Differs from Common Tern by darker grey underparts, all-black bill at all seasons, and diagnostic dark secondary underwing bar; the non-breeding Common Tern shows a dark primary bar but lacks the secondary bar of Aleutian Tern.
Pelagic and occasionally coastal seas.
Feeds by plunge-diving. Often perches on floating objects and debris. Generally silent on passage.