Sula dactylatra
masked booby

Masked boobies are fairly widespread; they are found primarily in the Atlantic and Pacific oceans. In the United States they are restricted to the three Hawaiian islands of Lehau, Moku Manu and Kaula. They are found mainly in the tropics. Masked boobies are found off the Yucatan peninsula and in much of South America. There are a variety of boobies with different ranges, but masked boobies are found on many islands between 30 degrees N and 30 degrees S, with tiny habitats from the Pacific to the Red Sea, and even on islands near Indonesia and Australia. (Anderson, 1993)

Boobies prefer to live on small, flat islands without trees. They often nest on the edges of cliffs or in flat areas that allow for easy take-off. They spend much of their time foraging over the ocean far from land. (Anderson, 1993)

Masked boobies are graceful birds, their body is white, they have black on thier wings and tails and a black mask around their beak and eyes. They are the biggest species of boobies. Females are larger than males, ranging from 75 to 86 cm long, males are from 74 to 82 cm long. They weigh from 1220 to 2353 g and have wingspans of 152 cm, on average. It is difficult to tell males and females apart because they both have bright white plumage as adults; young boobies are often mistaken for northern gannets (Sula bassanus). Masked boobies are born naked but are completely covered with feathers after 35 to 40 days. Juveniles are grey with white underparts and do not look like adults until their fourth year. (Anderson, 1993; National Wildlife Refuge, 2000)

Boobies have intricate mating rituals; males attract females by stretching out their necks and presenting gifts such as small stones and feathers to their perspective mates. After a slow walk they copulate; copulation takes ten to twenty seconds, and the female begins incubating immediately after laying the first egg. (Anderson, 1993)

Breeding seasons vary widely throughout the range of masked boobies; they can occur from February to August, January to July, and August to March. Masked boobies nest colonially; their nests are small hollows in the ground. The female usually lays two eggs. Incubation lasts 43 days on average. Masked boobies do not have brood patches, so they incubate the eggs with their feet. The first chick to hatch kicks the second chick out of the nest, so parents raise only one offspring. The chick fledges in 109 to 151 days and is intependent in one to two months. Juveniles reach sexual maturity in 3 to 5 years. (Anderson, 1993; National Wildlife Refuge, 2000)

Both males and femles incubate the eggs. The first chick to hatch kicks the second chick out of the nest, so the parents only raise one offspring. Chicks are usually fed only once or twice a day. Both parents feed their young, but females may bring more food to the nest than males. Both parents continue to protect and feed their chick for one to two months after it fledges. (Kepler, 1969; National Wildlife Refuge, 2000)

Masked Boobies have a lifespan of 15 to 20 years; the longest known lifespan is 20 years. (Anderson, 1993; Kepler, 1969; National Wildlife Refuge, 2000)

Masked boobies usually nest colonially. They are quick to sound an alarm if suprised or threatened but are not aggressive and are sometimes friendly to humans. Masked boobies spend most of their time out at sea in search of food. They usually feed diurnally. (Anderson, 1993)

We do not have information on home range for this species at this time.

Males have a high-pitched whistle while females have a more "honky" sounding call. Males will communicate by calling during their courtship displays or when they are frightened or alarmed. Females only call for help and as a warning. Both sexes are usually silent at night. (Anderson, 1993)

Boobies have a diet consisting mostly of fish and squid. They catch their prey by diving from heights of up to 30 m. When collecting food for offspring, boobies usually tend to stay closer to land, otherwise they hunt around 65 km from shore. (Anderson, 1993; National Wildlife Refuge, 2000)

There are no known predators of masked boobies. Because they are not usually found in dense populations and because they nest on islands, it might be hard for predators to rely on them as prey. (Great Barrier Reef - Reef Education, 1996)

Because masked boobies do not occur in dense populations, they do not seriously affect fish populations where they feed, nor are they important food sources for predators. (Anderson, 1993)

Fishermen sometimes find schools of tuna by following feeding boobies; without knowing it, boobies provide fisherman with information on the best places to find fish. Boobies are also popular among birdwatchers. (Anderson, 1993)

There are no known adverse affects of masked boobies on humans.

Interactions with humans seem to have had little effect on the species. Thousands of tourists pass close by their nests in the Galapagos, seemingly without any negative effects. Though there have been a few cases of boobies caught in fishing traps, these numbers are reportedly small. (Anderson, 1993)