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Masked booby

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Masked booby
Masked booby with chick.JPG
Austropacific masked booby (S. d. personata) with chick (background)
Scientific classification edit
Kingdom: Animalia
Phylum: Chordata
Class: Aves
Order: Suliformes
Family: Sulidae
Genus: Sula
S. dactylatra
Binomial name
Sula dactylatra
(Lesson, 1831)

see text

Sula dactylatra - MHNT

The masked booby (Sula dactylatra) is a large seabird of the booby family, Sulidae. First described by French naturalist René-Primevère Lesson in 1831, the masked booby is one of six species of booby in the genus Sula. This species breeds on islands in tropical oceans, except in the eastern Atlantic; in the eastern Pacific it is replaced by the Nazca booby, Sula granti, which was formerly regarded as a subspecies of masked booby.[2][3] It is also called the masked gannet or the blue-faced booby.

The masked booby nests in small colonies, laying two chalky white eggs on sandy beaches in shallow depressions. The first chick usually kills the second one.


French naturalist René-Primevère Lesson described the masked booby in 1829 in Louis Isidore Duperrey's work Voyage autour du Monde, Exécuté par Ordre du Roi, Sur la Corvette de Sa Majesté, La Coquille, pendant les années 1822, 1823, 1824 et 1825, after encountering it in Ascension Island in the South Atlantic.[4] The species name is from the Ancient Greek word dactyl "finger" and Latin ater "black". "Black fingers" refers to the splayed wingtips in flight.[5] Swedish zoologist Carl Jakob Sundevall described it as Sula cyanops in 1837, the species name derived from the Ancient Greek words cyanos "blue",[6] and ops "face".[7]

John Gould described Sula personata in 1846 from Australia,[8] the species name being the Latin adjective personata "masked".[9] Gould adopted the name Sula cyanops in his 1865 Handbook to the Birds of Australia.

Sundevall's binomial name was followed as Lesson's 1829 record did not sufficiently describe the species, however Australian amateur ornithologist Gregory Mathews pointed out that although Lesson's 1829 account did not describe the bird, his 1831 account did and thus predated Sundevall by six years, and hence Sula dactylactra had priority.[10] The American Ornithological Union followed in their 17th supplement to their checklist in 1920.[11]

"Masked booby" has been designated the official name by the International Ornithologists' Union (IOC).[12] It has also been called masked gannet, blue-faced booby, white booby (for its plumage), and whistling booby (for its distinctive call).[5]

The masked booby is one of six species of booby in the genus Sula.[12] A genetic study using both nuclear and mitochondrial DNA showed the Masked and Nazca boobies to be each other's closest relatives, their lineage diverging from a line that gave rise to the blue-footed and Peruvian boobies. The masked and Nazca boobies were divergent enough to indicate the latter, formerly regarded as a subspecies of the former, should be classified as a separate species. Molecular evidence suggests they most likely diverged between 0.8 and 1.1 million years ago. Complex water currents in the eastern Pacific may have established an environmental barrier leading to speciation.[13]

There is a clinal change in size across its range, where birds in the Atlantic are the smallest, with the size increasing westwards to the eastern Pacific, where the largest individuals are found.[14] Four subspecies are recognized by the IOC.[12]

  • S. d. personata Gould, 1846: Austropacific masked booby
Breeds in the central and western Pacific and around Australia, as well as off Mexico and on Clipperton Island. Birds of the latter two locations have been separated as subspecies californica, and the north west Australian population has been named as subspecies bedouti, but neither is usually considered valid.[12]
  • S. d. dactylatra Lesson, 1831: Atlantic masked booby
Breeds in the Caribbean and some Atlantic islands including Ascension Island. It has recently started breeding off Tobago, formerly being known in this area only from a single sight record from an oil rig off Trinidad.
  • S. d. melanops Hartlaub, 1859: Western Indian Ocean masked booby
Breeds in the western Indian Ocean.[15] Hartlaub described this taxon in 1859 from Maydh Island off the coast of Somalia near Maydh. He noted its black mask and blue-grey feet to be distinct from Sundevall's cyanops with a blue face, and Lesson's dactylatra with yellow feet.[16] The subspecies name is derived from the Ancient Greek words mela(no)s "black",[17] and ops "face".
  • S. d. tasmani (including S. d. fullagari) van Tets, Meredith, Fullagar & Davidson, 1988: Tasman booby or Lord Howe masked booby
The form breeding on Lord Howe and the Kermadec Islands. New Zealand naturalist Walter Oliver had noted that this bird had dark brown rather than pale irises since 1930, but it was not until 1990 that it was formally investigated by O'Brien and Davies and found to have longer wings than other populations as well. They classified it as a new subspecies—S. d. fullagari—in 1990.[18] Meanwhile, large prehistoric specimens known from the former and Norfolk Island were classified as a separate species—S. tasmani—in 1988, thought to have become extinct from Polynesian and then European seafarers and settlers.[19] However, Holdaway and colleagues cast doubt on the distinctness of the fossil taxon in 2001,[20] and a 2010 review by Tammy Steeves and colleagues of the fossil material and DNA found the two overlapped considerably, and hence the extinct and living entities were found to be the same taxon, now known as S. d. tasmani as it has priority over S. d. fullagari.[21] Fieldwork in the Kermadec Islands indicates the bills of adults are bright yellow, and that adult males had brighter yellow feet than females.[22]


The largest species of booby, the masked booby ranges from 75 to 85 cm (30 to 33 in) long, with a 160–170 cm (63–67 in) wingspan and 1.2–2.2 kg (2.6–4.9 lb) weight. It has a typical sulid body shape, with a long pointed bill, long neck, aerodynamic body, long slender wings and pointed tail. The adult is almost wholly bright white with a dark face mask. The sexes have similar plumage, and there is no seasonal variation.[23] The bill is yellow while the bare skin around the face, thoat and lores is black.[24] The wings and tail are brown-black, the individual feathers are dark with white bases and shafts. The underwing is white.[25]

The juvenile is a streaked or mottled grey-brown on the head and upperparts, with a whitish neck collar. The wings are dark brown and underparts are white. Its bill is yellowish, face is blue-grey and iris a dark brown. Older immature birds have a broader white collar and rump.[23] Full adult plumage is acquired three to four months before the bird turns three years old.[24]

Masked Booby Juvenile off Goa Coast

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.

Distribution and habitat

The masked booby is found across tropical oceans between the 30th parallel north and 30th parallel south. In the Indian Ocean it ranges from the coastlines of the Arabian Peninsula and East Africa across to Sumatra and Western Australia, though it is not found off the coast of the Indian subcontinent. Off the Western Australian coastline it is found as far south as Dampier Arch. In the Pacific, it ranges from Brisbane eastwards. It is found in the Caribbean and Atlantic Ocean south to Ascension Island.[26]

During monsoon season (midyear), the masked booby is an occasional vagrant along the western coast of India, with records from Kerala, Karnataka, and Maharashtra states.[27]

It is a vagrant to the Caroline Islands.[28]


The masked booby is a fairly sedentary bird, wintering at sea, but rarely seen far away from the breeding colonies. However, Caribbean birds occasionally wander north to warm southern Gulf Stream waters off the eastern seaboard of the United States. More remarkably, there have been three western Palaearctic records of masked booby, presumably dactylatra, all from Spanish waters, although one of these also entered French territorial areas.

The masked booby generally flies at least 7 m (23 ft) in height, and at speeds of up to 70 km/h (43 mph). It alternates between gliding and active flying with strong periodic wingbeats.[23]


Egg and chick in nest

The masked booby nests in small colonies, laying two chalky white eggs on sandy beaches in shallow depressions, with an interval of five to eight days between the laying of each egg.[29] Occasionally nests with three eggs are reported; these are due to an egg from another nest rolling downhill into the nest.[29]

The eggs are incubated by both adults for 45 days.

In most cases, the first chick will kill its smaller, weaker sibling after it hatches.[30] Siblicide has been well studied in this species; researchers such as David Anderson have demonstrated that while the boobies can manage to feed two chicks if siblicide is prevented, they do so at a steep penalty to health and future reproductive success.[31][32][33]

Compared to other species of boobies such as the blue-footed booby, siblicide is obligatory in the masked booby. One reason is because the masked boobies build very shallow flat nests, so older chicks can expel their younger siblings with relative ease. Blue-footed booby parents, meanwhile, build nests with steeper sides, thus preventing some older chicks from engaging in siblicidal behaviour.[34]


The masked booby is a spectacular diver, plunging vertically or near-vertically from heights of anywhere from 12 to 100 m (but more commonly 15 to 35 m) above the water into the ocean at high speed, to depths of up to 3 m (120 in).[35]

Fish, particularly flying fish, up to 28 cm (11 in) long (rarely up to 41 cm (16 in)) form the bulk of its diet, along with cephalopods.[14] Species eaten include yellowtail amberjack (Seriola lalandi), skipjack tuna (Katsuwonus pelamis), various species of flying fish, mullet of the genus Mugil, and others.[36]

The masked booby forages with the white-bellied storm petrel and Bulwer's petrel at times.[37] Frigatebirds often harass the species till they disgorge their catch and steal their food.[14]


  1. ^ BirdLife International (2012). "Sula dactylatra". IUCN Red List of Threatened Species. Version 2013.2. International Union for Conservation of Nature. Retrieved 26 November 2013.
  2. ^ Pitman, R. L.; Jehl, J. R. (1998): Geographic variation and reassessment of species limits in the "Masked" Boobies of the eastern Pacific Ocean. Wilson Bulletin 110(2): 155-70
  3. ^ Friesen, V. L.; Anderson, D. J.; Steeves, T. E.; Jones, H. & Schreiber, E. A. (2002): Molecular Support for Species Status of the Nazca Booby (Sula granti). Auk 119(3): 820–26. [English with Spanish abstract] DOI: 10.1642/0004-8038(2002)119[0820:MSFSSO]2.0.CO;2 PDF fulltext Archived 2006-05-23 at the Wayback Machine
  4. ^ Lesson, René-Primevère (1829). Duperrey, Louis Isidore, ed. Voyage autour du Monde, Exécuté par Ordre du Roi, Sur la Corvette de Sa Majesté, La Coquille, pendant les années 1822, 1823, 1824 et 1825. Zoologie. 1. Paris: Arthus Bertrand. p. 494.
  5. ^ a b Gray, Jeannie; Fraser, Ian (2013). Australian Bird Names: A Complete Guide. Collingwood, Victoria: Csiro Publishing. p. 151. ISBN 978-0-643-10471-6.
  6. ^ Liddell & Scott 1980, p. 397.
  7. ^ Liddell & Scott 1980, p. 804.
  8. ^ Gould, John (1846). "Descriptions of eleven new species of Australian birds". Proceedings of the Zoological Society of London. 14: 18–21. doi:10.1111/j.1469-7998.1846.tb00135.x.
  9. ^ Simpson, D.P. (1979). Cassell's Latin Dictionary (5th ed.). London: Cassell Ltd. p. 442. ISBN 0-304-52257-0.
  10. ^ Mathews, Gregory (1911). "On some necessary alterations in the nomenclature of birds". Novitates Zoologicae. 18: 9–10.
  11. ^ "Seventeenth Supplement to the American Ornithologists' Union Check-List of North American Birds" (PDF). The Auk. 37 (3): 439–49. 1920. doi:10.2307/4073271.
  12. ^ a b c d Gill, Frank; Donsker, David, eds. (2017). "Hamerkop, Shoebill, pelicans, boobies, cormorants". World Bird List Version 7.1. International Ornithologists' Union. Retrieved 31 January 2018.
  13. ^ Patterson, S.A.; Morris-pocock, J.A.; Friesen, V.L (2011). "A multilocus phylogeny of the Sulidae (Aves: Pelecaniformes)". Molecular Phylogenetics and Evolution. 58 (2): 181–91. doi:10.1016/j.ympev.2010.11.021. PMID 21144905.
  14. ^ a b c Orta, J.; Jutglar, F.; Garcia, E.F.J.; Kirwan, G.M.; Boesman, P. (2017). del Hoyo, Josep; Elliott, Andrew; Sargatal, Jordi; Christie, David A.; de Juana, Eduardo, eds. "Masked booby (Sula dactylatra)". Handbook of the Birds of the World Alive. Barcelona, Spain: Lynx Edicions. (Subscription required (help)). Missing or empty |url= (help); |access-date= requires |url= (help)
  15. ^ Redman, Nigel; Stevenson, Terry; Fanshawe, John (2016). Birds of the Horn of Africa: Ethiopia, Eritrea, Djibouti, Somalia, and Socotra - Revised and Expanded Edition. Princeton Field Guides. Princeton, New Jersey: Princeton University Press. p. 44. ISBN 978-0-691-17289-7. OCLC 944380248. Retrieved 2018-12-04.
  16. ^ Hartlaub, G. (1859). "List of birds observed and collected during a voyage in the Red Sea". The Ibis. 1 (4): 337-52 [351-52].
  17. ^ Liddell & Scott 1980, p. 431.
  18. ^ O'Brien, R.M.; Davies, J. (1990). "A new subspecies of Masked Booby Sula dactylatra from Lord Howe, Norfolk and Kermadec Islands" (PDF). Marine Ornithology. 18 (1): 1–7.
  19. ^ van Tets, Gerard Frederick; Meredith, C.W.; Fullagar, P.J.; Davidson, P.M. (1988). "Osteological differences between Sula and Morus, and a description of an extinct new species of Sula from Lord Howe and Norfolk Islands, Tasman Sea" (PDF). Notornis. 35: 35–57.
  20. ^ Holdaway, Richard; Anderson, Atholl (2001). "Avifauna from the Emily Bay Settlement Site, Norfolk Island: A Preliminary Account" (PDF). Records of the Australian Museum Supplement. 27: 85–100.
  21. ^ Steeves, Tammy E.; Holdaway, Richard N.; Hale, Marie L.; McLay, Emma; McAllan, Ian A. W.; Christian, Margaret; Hauber, Mark E.; Bunce, Michael (2010). "Merging ancient and modern DNA: extinct seabird taxon rediscovered in the North Tasman Sea". Biology Letters. 6 (1): 94–97. doi:10.1098/rsbl.2009.0478. PMC 2817237.
  22. ^ Ismar, Stefanie M. H.; Baird, Karen; Patel, Selina; Millar, Craig D.; Hauber, Mark E. (2010). "Morphology of the recently re-classified Tasman Masked Booby Sula dactylatra tasmani breeding on the Kermadec Islands" (PDF). Marine Ornithology. 38 (2): 105–09.
  23. ^ a b c Marchant & Higgins 1990, p. 763.
  24. ^ a b Marchant & Higgins 1990, p. 771.
  25. ^ Marchant & Higgins 1990, p. 770.
  26. ^ Marchant & Higgins 1990, p. 764.
  27. ^ Kasambe, Raju (2010). "Recent records of masked booby (Sula dactylatra) along the western coast of India". Newsletter for Birdwatchers. 50 (4): 59–60.
  28. ^ Wiles, G.J.; Worthington, D.J.; Beck, Jr., R.E.; Pratt, H.D.; Aguon, C.F.; Pyle, R.L. (2000). "Noteworthy Bird Records for Micronesia, with a Summary of Raptor Sightings in the Mariana Islands, 1988–1999" (PDF). Micronesica. 32 (2): 257–84.
  29. ^ a b Marchant & Higgins 1990, p. 769.
  30. ^ Mack, Alison. 1997. "Natural born killers." Earth 6, no. 3: 12. General Science Collection, EBSCOhost (accessed May 4, 2007).
  31. ^ Anderson, David J. 1990. "Evaluation of Obligate Suicide in Boobies. 1. A Test of the Insurance-Egg Hypothesis." The American Naturalist 135, vol. 3: 334-350
  32. ^ Anderson, David J. 1990. "Evolution of Obligate Siblicide in Boobies. 2: Food Limitation and Parent-Offspring Conflict" Evolution 44 no. 8: 2069–2082
  33. ^ Alda, Alan (Host). (1999). Voyage to the Galapagos [Television series episode]. Scientific American Frontiers. Arlington, Virginia: Public Broadcasting Service. (transcript here:
  34. ^ Anderson, David J. (1995). "The Role of Parents in Siblicidal Brood Reduction of Two Booby Species". The Auk. 112 (4): 860–869. doi:10.2307/4089018.
  35. ^ Marchant & Higgins 1990, p. 765.
  36. ^ Marchant & Higgins 1990, p. 766.
  37. ^ Ainley, David G.; Boekelheide, Robert J. (1984). "An Ecological Comparison of Oceanic Seabird Communities of the South Pacific Ocean". Studies in Avian Biology. 8: 2–23.

Cited texts