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Sula dactylatramasked booby

By Paul Mansoor

Ge­o­graphic Range

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)

Habi­tat

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)

Phys­i­cal De­scrip­tion

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 (Morus 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)

  • Sexual Dimorphism
  • sexes alike
  • female larger
  • Range mass
    1220 to 2353 g
    43.00 to 82.93 oz
  • Range length
    74 to 86 cm
    29.13 to 33.86 in
  • Average wingspan
    152 cm
    59.84 in
  • Average basal metabolic rate
    5.5209 W
    AnAge

Re­pro­duc­tion

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)

  • Breeding season
    Breeding seaons vary widely throughout the range of masked boobies.
  • Range eggs per season
    1 to 2
  • Average eggs per season
    1
  • Average eggs per season
    1
    AnAge
  • Average time to hatching
    43 days
  • Range fledging age
    109 to 151 days
  • Range time to independence
    1 to 2 months
  • Range age at sexual or reproductive maturity (female)
    3 to 5 years
  • Range age at sexual or reproductive maturity (male)
    3 to 5 years

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)

  • Parental Investment
  • no parental involvement
  • altricial
  • pre-hatching/birth
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifes­pan/Longevity

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)

Be­hav­ior

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)

Home Range

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

Com­mu­ni­ca­tion and Per­cep­tion

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)

Food Habits

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)

  • Animal Foods
  • fish
  • mollusks

Pre­da­tion

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)

Ecosys­tem Roles

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)

Eco­nomic Im­por­tance for Hu­mans: Pos­i­tive

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)

Eco­nomic Im­por­tance for Hu­mans: Neg­a­tive

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

Con­ser­va­tion Sta­tus

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)

Con­trib­u­tors

Alaine Cam­field (ed­i­tor), An­i­mal Di­ver­sity Web.

Paul Man­soor (au­thor), Uni­ver­sity of Michi­gan-Ann Arbor, Phil Myers (ed­i­tor), Mu­seum of Zo­ol­ogy, Uni­ver­sity of Michi­gan-Ann Arbor.

Glossary

Australian

Living in Australia, New Zealand, Tasmania, New Guinea and associated islands.

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Ethiopian

living in sub-Saharan Africa (south of 30 degrees north) and Madagascar.

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Neotropical

living in the southern part of the New World. In other words, Central and South America.

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acoustic

uses sound to communicate

altricial

young are born in a relatively underdeveloped state; they are unable to feed or care for themselves or locomote independently for a period of time after birth/hatching. In birds, naked and helpless after hatching.

bilateral symmetry

having body symmetry such that the animal can be divided in one plane into two mirror-image halves. Animals with bilateral symmetry have dorsal and ventral sides, as well as anterior and posterior ends. Synapomorphy of the Bilateria.

carnivore

an animal that mainly eats meat

chemical

uses smells or other chemicals to communicate

coastal

the nearshore aquatic habitats near a coast, or shoreline.

colonial

used loosely to describe any group of organisms living together or in close proximity to each other - for example nesting shorebirds that live in large colonies. More specifically refers to a group of organisms in which members act as specialized subunits (a continuous, modular society) - as in clonal organisms.

diurnal
  1. active during the day, 2. lasting for one day.
ecotourism

humans benefit economically by promoting tourism that focuses on the appreciation of natural areas or animals. Ecotourism implies that there are existing programs that profit from the appreciation of natural areas or animals.

endothermic

animals that use metabolically generated heat to regulate body temperature independently of ambient temperature. Endothermy is a synapomorphy of the Mammalia, although it may have arisen in a (now extinct) synapsid ancestor; the fossil record does not distinguish these possibilities. Convergent in birds.

iteroparous

offspring are produced in more than one group (litters, clutches, etc.) and across multiple seasons (or other periods hospitable to reproduction). Iteroparous animals must, by definition, survive over multiple seasons (or periodic condition changes).

molluscivore

eats mollusks, members of Phylum Mollusca

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

native range

the area in which the animal is naturally found, the region in which it is endemic.

nomadic

generally wanders from place to place, usually within a well-defined range.

oceanic islands

islands that are not part of continental shelf areas, they are not, and have never been, connected to a continental land mass, most typically these are volcanic islands.

oriental

found in the oriental region of the world. In other words, India and southeast Asia.

World Map

oviparous

reproduction in which eggs are released by the female; development of offspring occurs outside the mother's body.

pelagic

An aquatic biome consisting of the open ocean, far from land, does not include sea bottom (benthic zone).

piscivore

an animal that mainly eats fish

saltwater or marine

mainly lives in oceans, seas, or other bodies of salt water.

sexual

reproduction that includes combining the genetic contribution of two individuals, a male and a female

social

associates with others of its species; forms social groups.

tactile

uses touch to communicate

terrestrial

Living on the ground.

tropical

the region of the earth that surrounds the equator, from 23.5 degrees north to 23.5 degrees south.

visual

uses sight to communicate

year-round breeding

breeding takes place throughout the year

Ref­er­ences

An­der­son, D. 1993. Sula dacty­la­tra - Masked Booby. The Birds of North Amer­ica, No. 73, 1993: 1-16.

Great Bar­rier Reef - Reef Ed­u­ca­tion, 1996. "GBR Ex­plorer - Boo­bies" (On-line). Boo­bies. Ac­cessed April 20, 2004 at http://​www.​reefed.​edu.​au/​explorer/​animals/​marine_​vertebrates/​seabirds/​boobies.​html.

Ke­pler, C. 1969. Breed­ing Bi­ol­ogy of the Blue-Faced Booby on Green Is­land, Kure Atoll. Cam­bridge, MA: Nut­tall Or­nitho­log­i­cal Club.

Na­tional Wildlife Refuge, 2000. "Masked Booby" (On-line). Ac­cessed April 20, 2004 at http://​midway.​fws.​gov/​wildlife/​mabo.​html.

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Classification

Classification

  • Kingdom Animalia animals
  • Phylum Chordata chordates
  • Subphylum Vertebrata vertebrates
  • Class Aves birds
  • Order Pelecaniformes pelicans, tropicbirds, cormorants, and relatives
  • Family Sulidae gannets and boobies
  • Genus Sula boobies
  • Species Sula dactylatra masked booby