Sula dactylatra is a large seabird found in tropical regions, from the family of Sulidae. This bird has an overall white plumage with black feathers on its wings and tail. It also possesses a black ‘mask’ that surrounds its yellow eyes and has a distinctive stout and horn coloured bill; hence also commonly known as the Blue-faced booby. Its size ranges from 81 to 92 cm. Females are usually larger in size than males but are otherwise similar in appearance. They can easily be confused with the adult Red footed booby, from which they differ for their black and not white tail. Masked boobies make hissing and honking noises during display but are silent while at sea.
Nestlings are usually naked but are entirely feathered by 40 days. Young ones have white and grey plumage until they reach their 4th year. Juveniles look similar to juvenile brown boobies but are larger and possess an obvious white colour and pale patch on their backs.
The masked booby has an affinity for deeper waters and is found over pelagic (open sea) areas of the ocean. It can be seen on almost every coast worldwide with the exception of the Eastern Atlantic, Northern Indian Ocean and Central-Eastern Pacific regions. Its diet constitutes of shoaling fish, flying fish and large squid. It is not known to migrate.
Breeding season varies with respect to region and the adults aggregate in groups, forming colonies. Breeding usually occurs on Serpent Islet, off the north coast of Mauritius during the months of October and November,. Blue faced boobies’ nest on flat ground, avoiding steep slopes or vegetation.
Although listed as ‘Least Concern’ by the IUCN, this species population has not been scientifically quantified. It is presumed to be declining due to high levels of predation and over exploitation .
Masked boobies are one of the best divers, they can reach down to 100m depth. They fold their wings into their bodies and plunge deep into water to catch their prey.
They are the biggest known boobies.
They also breed in the Seychelles and the Mascarenes.
 ‘Geographic Variation and Ecology of Three Pantropical Seabirds’.