The masked Booby (Sula dactylatra), is a large seabird of the gannet family, Sulidae. This is a bird of tropical waters and breeds on islands in all tropical oceans except the eastern Atlantic. This is a fairly sedentary bird that winters at sea and is rarely seen far from its breeding grounds. Some Caribbean birds wander north to warm southern Gulf Stream waters off the eastern seaboard of the United States.
It is the largest booby, attaining 32 to 36 inches in length with a 60 inch wingspan. The average weight is 3.3 pounds. (53 oz.). Adults are white with pointed black wings, a pointed black tail, and a dark gray facemask. Sexes are similar, but the male has a yellow bill, while the female’s is greenish yellow. During the breeding season they have a patch of bare, bluish skin at the base of its bill. The young are brownish on the head and upperparts, with a whitish rump and neck collar. The underparts are white.
These birds nest in small colonies and lay two off-white eggs on sandy beaches in shallow recessions. Both male and female incubate the eggs for 45 days. In most cases, the first to hatch will kill the smaller weaker sibling as it hatches. This practice is known as siblicide and has been well studied in this species. It is also well documented that this practice is necessary in the survival of the species for future reproductive success.
The Masked Booby is silent at sea, but has a reedy whistling greeting call at the nesting colonies. While on the breeding grounds, these birds display a wide range of hissing and quacking notes. Masked Boobies are spectacular divers, plunging diagonally into the ocean at high speed. They mainly eat small
fish, including flying fish.