Masked Booby | Sula dactylatra

Voice

Silent at sea. At the colony the male gives a thin whistle, the female a loud, hoarse honking honk.

Identification

Large and robust, with a thick, pointed yellow bill, a black bare mask around the bill base and eye, and grey-green feet. The adult is brilliant white with black primaries and secondaries, so the whole trailing edge of the wing is black, black greater coverts at the shoulder and a black tail. The western Indian Ocean form (melanops) has a dark underwing border and a yellowish bill. Juveniles have a brown head and upperparts with a white collar and pale fringes, white underparts and a white underwing with dark borders; they turn white over two to three years. Flies with deep, powerful beats and often dives steeply from a great height.

Confusion species

Northern Gannet (Morus bassanus) is larger, with white secondaries and tail and a yellow head; the two hardly overlap in the region. White-morph Red-footed Booby (Sula sula) is smaller, with a white tail, red feet and a black carpal patch on the underwing. Juvenile Brown Boobies (Sula leucogaster) have a brown breast and no white collar. Red-billed Tropicbird (Phaethon aethereus) is also white and black, but much smaller, with a red bill and fine black barring on the back.

Habitat

Open, deep sea, often far offshore, over upwelling areas and places with shoals of flying fish and sardines. Breeds on the ground on bare, flat islands and rock plateaus. Rests on the water, on islets and sometimes on ships and fish-farm cages.

Range and movements

Oman: breeds in large numbers on the Hallaniyat (Kuria Muria) Islands off the coast of Dhofar; common year-round at sea off Dhofar, around Masirah and to Ras al-Hadd, scarcer in the Gulf of Oman. Yemen: regular at sea in the Gulf of Aden and around Socotra, where there may also be small colonies. United Arab Emirates: scarce visitor, 46 sightings between 1973 and 2022, mainly off Fujairah and Dibba on the Gulf of Oman. Kuwait: one at Al Jahra in April 2015. Rare in the southern Red Sea; a vagrant further north, with one sighting in Egyptian waters in 2019. On the Atlantic coast of Morocco a dead bird was found between Tan-Tan and Chbika in January 2006. Elsewhere it breeds on tropical islands in all oceans, in the Indian Ocean from the Seychelles and Chagos to Western Australia.

• Resident
• Summer visitor (c. Apr–Sep)
• Winter visitor (c. Oct–Mar)
• Passage (Mar–Apr, Oct–Nov)
• dark = core range, pale = thinly spread

How and when to look

In summer and autumn they are often seen from the Dhofar coast, for example at Mirbat and Ras Hamar, and above all on pelagic trips off Mirbat. The best time is the first hours of the morning, when birds move along the coast from the open sea.

Conservation status

Not globally threatened. The Arabian breeding population is small and concentrated on a few islands, making it vulnerable to disturbance, introduced predators, oil pollution and bycatch in gill nets and longlines. The Hallaniyat Islands are on the World Heritage tentative list, partly because of this colony.

Scientific name

Sula dactylatra | Lesson, 1831

Lesson described the species in 1831 and placed it straight away in the genus where it still stands. The genus Sula was introduced in 1760 by Brisson. Sula goes back to súla, the Old Norse and Icelandic word for the gannet; the name passed to the boobies. dactylatra combines Greek daktulos 'finger' and Latin ater 'black': 'black fingers', after the splayed black wingtips in flight. The specimen the first description was based on came from Ascension Island (South Atlantic).