Masked booby
Largest booby species, known for plunge diving and sibling rivalry.
The masked booby (Sula dactylatra), also known as the masked gannet or blue-faced booby, is a large seabird belonging to the Sulidae family, which includes boobies and gannets. French naturalist René-Primevère Lesson first described it in 1831, and it is one of six species in the genus Sula. It is the biggest of all booby species, with a typical sulid build: a long, pointed yellowish bill, a long neck, a streamlined body, long slender wings, and a pointed tail. Adults are bright white with black wings, a black tail, and a dark face mask; they measure 75–85 cm (30–33 in) in length. Males and females look alike. This species lives across tropical oceans, but not in the eastern Atlantic or eastern Pacific, where the Nazca booby (Sula granti)—once considered a subspecies of the masked booby—takes its place.
Nesting occurs in colonies, usually on remote islands and atolls far from mainland areas, close to the deep water needed for feeding. During breeding, masked boobies are territorial and use aggressive displays to defend their nests. Potential and established pairs perform courtship and greeting rituals. The female lays two chalky white eggs in a shallow depression on flat, bare ground away from plants. Chicks hatch featherless but quickly grow white down. The second chick usually dies, killed by its older sibling. These birds are spectacular plunge divers, hitting the ocean at high speed to catch prey, mainly flying fish. They also eat squid. The species faces few threats; although its population is declining, the International Union for Conservation of Nature (IUCN) lists it as a least-concern species.
**Taxonomy** René Lesson, a French naturalist, served on the crew of the *La Coquille* under Captain Louis Isidore Duperrey during a round-the-world voyage from August 1822 to March 1825. Lesson wrote the ornithological sections of Duperrey’s multi-volume publication about the trip. In his 1829 account of a visit to Ascension Island in the South Atlantic, Lesson mentioned seeing masked boobies and, in a footnote, proposed the binomial name *Sula dactylatra*. He then formally described the species in 1831. The specific name comes from the Ancient Greek *dáktulos* (finger) and Latin *ater* (black), referring to the black-tipped wing feathers that spread like fingers in flight. In 1837, Swedish zoologist Carl Jakob Sundevall described the species as *Dysporus c
- Scientific name
- Sula dactylatra
- Family
- Sulidae
- Length
- 75–85 cm (30–33 in)
- Wingspan
- 160–170 cm (63–67 in)
- Weight
- 1.2–2.2 kg (2.6–4.9 lb)
- First described by
- René-Primevère Lesson, 1831
- IUCN status
- Least concern
Lore & Background
The masked booby was first formally described by French naturalist René-Primevère Lesson in 1831, based on his encounter with the species on Ascension Island during a voyage around the world. The specific epithet dactylatra combines Ancient Greek for 'finger' and Latin for 'black', referring to the splayed wingtips in flight. The species has also been described under other names, including Dysporus cyanops by Carl Jakob Sundevall in 1837 and Sula personata by John Gould in 1846, but Lesson's name has priority.
Reader's Guide
The masked booby is significant as the largest species of booby and a widespread tropical seabird. Its taxonomy has been clarified through genetic studies, which showed that the Nazca booby, formerly considered a subspecies, is a separate species that diverged between 0.8 and 1.1 million years ago. The species exhibits clinal size variation, with Atlantic birds smallest and Indian Ocean birds largest. Four subspecies are recognized, including the Tasman booby (S. d. tasmani), which was once thought extinct but is now known to be the same as living populations. The masked booby is a spectacular plunge diver, feeding mainly on flying fish and squid, and nests in colonies on remote islands. Despite a declining population, it is considered a least-concern species by the IUCN.
Did You Know?
- The masked booby is the largest species of booby, ranging from 75 to 85 cm in length.
- The second chick born generally does not survive and is killed by its elder sibling.
- Subfossil bones 14,000 years old belonging to the species have been found on St. Helena Island.
- The species has also been called the white booby and whistling booby.
More in Birds of the Indian Ocean 1-24
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