Sooty Tern

Onychoprion fuscatus
Sooty terns

The sooty tern, also commonly referred to as black-back sooty terns, is dark brown (appearing black) on its upper parts and white on its under parts. The forehead is white back to the eye and there is a black eye line from the bill to the back of the head. The tail is forked. Juveniles are dark sooty brown with buff feather edges and a white belly.

Sooty terns have been historically found to nest on Wilkes Island, the northern end of Peale Island, and along the northeastern side of the runway on Wake Island. In February 2007, a total of 192,000 nests were estimated; and, in January 2008, a total of 109,000 nests were estimated. Breeding takes place from April through September. Birds start to breed at 6-8 years of age. Highly ritualized and vocal aerial displays are conducted over nesting area prior to settling down to lay eggs. Nesting locations change slightly from season to season. A single speckled egg is laid on ground. No nest is prepared.

Incubation period averages 30 days. Individual incubation shifts are approximately 5 days. Heat stress may cause terns to abandon eggs for short periods to drink seawater. Sooty terns are easily disturbed by human activity, and repeated disturbance may result in permanent abandonment.

Chicks are shaded by parents during hot hours and brooded only when cool. Chicks are fed every 16 hours with regurgitated food. Parents locate chicks through vocalizations, and will feed only their own. Fledging occurs at about 8 weeks. Offspring continue to be fed by parents for several weeks after fledging.

Facts About Sooty Tern

Diet
Skim the water and take food on the wing, rarely touching down on the ocean. Poor oil glands, can become waterlogged if they alight on water for long duration. Feed offshore with predatory fish that drive smaller fish to the surface. Flying fish (primarily) and other fish constitute diet. Seem to feed extensively at night.
Life Span
32 years
Size
Length: 41-45 cm (16-18 in); wingspan: 86-94 cm (34-37 in)