Masked Booby (Sula dactylatra)

Masked Booby


The masked booby (Sula dactylatra), also called the masked gannet or the blue-faced booby, is a large seabird of the booby and gannet family, Sulidae. First described by the French naturalist René-Primevère Lesson in 1831, the masked booby is one of six species of booby in the genus Sula. It has a typical sulid body shape, with a long pointed yellowish bill, long neck, aerodynamic body, long slender wings and pointed tail. The adult is bright white with black wings, a black tail and a dark face mask; at 75–85 cm (30–33 in) long, it is the largest species of booby. The sexes have similar plumage. This species ranges across tropical oceans, except in the eastern Atlantic and eastern Pacific. In the latter, it is replaced by the Nazca booby (Sula granti), which was formerly regarded as a subspecies of masked booby. Juveniles of subsp personata on Kure Atoll in the Hawaiian island chain

Distribution And Habitat

The Masked Booby occurs throughout the worlds tropical and subtropical oceans (Raffaele and others 1998). It is a very rare and local year-round resident in the West Indies, where known breeding areas include the southern Bahamas, Jamaica, Puerto Rico, the Virgin Islands, Anguilla, Antigua, and the Grenadines (Raffaele and others 1998). It is described as uncommon in Puerto Rico and has been documented near Culebra, Monito (Oberle 2018), and Desecheo islands (McCandless 1958). It usually inhabits warm tropical waters out at sea (Oberle 2018), except when attending its nest (Raffaele and others 1998). The atlas fieldwork yielded a total of 10 records within six hexagons or 1 percent of the 479 total hexagons (see map). Of the six hexagons where this species was found, breeding met the atlas definition of confirmed in 50 percent (three) of the hexagons, while the species was observed in 50 percent (three) of the hexagons but without evidence of breeding (see map).Masked Booby distribution. The map shows the highest breeding code by hexagon and overlaying the ecological life zones in Puerto Rico. Note: percentages may not total 100 due to rounding.

Masked Booby Distribution

Breeding Habits

Previously published reports indicate that the Masked Booby generally breeds from February to August (Oberle 2018) and occasionally during September (Raffaele and others 1998). This is a colonial species, and the nest usually consists of a scrape cushioned with a fine layer 137Masked Booby/Boba Enmascaradaof weeds or grasses, usually made on the ground in small rocky islands (Biaggi 1997) or near a cliff face (Raffaele and others 1998). Atlas results show that this species breeds mostly from February to April, and to a lesser extent also during July and October (see chart). Overall, the breeding activity peaks in March, and it takes place on small offshore islands within the subtropical dry forest life zone (see chart). Results show that this species breeds in coastal areas within the subtropical dry forest life zone (100 percent of the hexagons) (see table and map).


The global population trend of the Masked Booby has not been quantified or assessed, but the species is described as fairly common (Stotz and others 1996), and it is currently listed as a species of least concern by the IUCN (BirdLife International 2018). Locally, this species is not listed in any of the threatened categories of PRDNER and USFWS. In Puerto Rico, the Masked Booby has a protected habitat in land of 2 percent or 1.5 km2 of the total area covered by the hexagons where evidence of breeding was found for this species (96 km2).