Nazca booby (Sula granti)

Description

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Nazca booby fact file

• Description
• Biology
• Range
• Habitat
• Status
• Threats
• Conservation
• Find out more
• Glossary
• References
• Print factsheet

Nazca booby description

With its bright orange coloured beak and eyes, contrasting plumage tones, and black, bare facial skin, the Nazca booby is one of the Galapagos Islands’ most charismatic bird species. Previously considered to be a subspecies of the more widespread masked booby (Sula dactylatra), the Nazca booby is now recognised as a distinct species ^{(3) (4)}. The head and body of the Nazca booby are almost entirely pristine white, except for the tail and the trailing edge of the wing, which are a rich, reddish tinged, chocolate brown ^{(3) (5)}. The bill colour varies between populations on different islands, but is usually bright orange in the male and rosy pink or pinkish-orange in the female. The iris is orange, and stands out in stark contrast against the surrounding black facial skin, while the bare skin of the feet and legs can vary from olive to blue-grey. Juvenile Nazca boobies have greyish-brown plumage on the back, head and neck with diffuse, pale flecking ⁽³⁾.

Size

Length: 81 – 92 cm ⁽²⁾

Nazca booby biology

Feeding in the near-shore waters surrounding oceanic islands, or along the coasts of Central and South America, the Nazca booby can be seen making dramatic plunge dives from heights of up to 30 metres into schools of fish ^{(3) (5) (6)}. Populations on the Galapagos mostly favour schools of sardines, but during El Niño years, when these fish are scarce, the birds will instead prey on flying fish ⁽³⁾.

The Nazca booby breeds at different times throughout the year according to the location of the nesting colony ⁽²⁾. A minimal nest is constructed with a few small pebbles laid on the ground, in which two eggs are laid a few days apart ⁽⁶⁾. Interestingly, incubation involves the parent bird wrapping both its feet around the sides and top of the eggs, transferring heat from the dense network of blood vessels in the webbing between the digits ⁽⁷⁾. Nazca booby chicks engage in siblicide, a behaviour in which the first chick to hatch after the 40-day incubation period invariably attacks the second chick and pushes it out of the nest ^{(6) (8)}. The parent birds ignore this battle and leave the second chick to die of starvation, or as a result of having its wounds pecked by blood-feeding birds such as mockingbirds and the large cactus-finch (Geospiza conirostris). The reason for such seemingly unnecessarily destructive behaviour is suggested to be because the second egg’s only purpose is to act as insurance in case the first egg does not hatch. Therefore, in cases where both eggs hatch, the second offspring could represent an extra energetic burden on the parent birds to feed it, particularly in years of low food supply ^{(8) (9)}. The remaining chick fledges after around 115 days ⁽⁶⁾, but does not reach sexual maturity and begin breeding until three to four years old ⁽³⁾.

Nazca booby range

The Nazca booby is found on and around several Pacific islands off the coast of Colombia, Ecuador and Central America. The largest nesting colonies occur on the Galapagos Islands located off the coast of Ecuador, and Malpelo Island, situated off the coast of Colombia, with much smaller numbers breeding on Isla La Plata and San Benedicto Island, located off the coasts of Ecuador and Mexico, respectively ⁽³⁾. In addition, Nazca boobies have recently been observed nesting on the Hawaiian Islands ⁽⁴⁾.

Nazca booby habitat

The Nazca booby nests on exposed cliff-tops and forages over tropical, coastal waters ⁽³⁾.

Nazca booby status

Classified as Least Concern (LC) on the IUCN Red List ⁽¹⁾.

Nazca booby threats

Like its close relative, the masked booby, some Nazca booby individuals are probably killed as a result of becoming entangled in fishing gear ⁽⁵⁾. Nevertheless, this species is relatively abundant at present and is not considered to be threatened ⁽¹⁾.

Nazca booby conservation

The Colombian conservation organisation, ProAves, is currently engaged in long-term population monitoring of the Nazca booby on Malpelo Island. By studying the biology, ecology and population structure of this species, they are helping to ensure that it is effectively managed and will remain abundant ⁽¹⁰⁾

View information on this species at the UNEP World Conservation Monitoring Centre.

Find out more

To learn more about conservation initiative for the Nazca booby visit:

• ProAves:
  www.proaves.org/article.php?id_article=560

For more information on this and other bird species please see:

• BirdLife International:
  http://www.birdlife.org

Authentication

Authenticated (17/07/09) by Dr. E. A. Schreiber, Research Associate, Bird Department of the Smithsonian National Museum of Natural History.

Glossary

El Niño

A natural phenomenon that happens every 4 to 12 years, and lasts for several months, when upwelling of cold, nutrient-rich water does not occur. This causes the warming of ocean surface water off the western coast of South America and causes die-offs of plankton and fish. It also affects Pacific jet stream winds, altering storm tracks and creating unusual weather patterns in various parts of the world.

Subspecies

A population usually restricted to a geographical area that differs from other populations of the same species, but not to the extent of being classified as a separate species.

References

1. IUCN Red List (June, 2009)
   http://www.iucnredlist.org
2. Swash, A., Still, R. and Lewington, I. (2005) Birds, mammals, and reptiles of the Galápagos Islands: an identification guide. Yale University Press, New Haven.
3. Pitman, R.L. and Jehl, J.R. (1998) Geographic variation and reassessment of species limits in the "Masked" Boobies of the eastern Pacific Ocean. The Wilson Bulletin, 110: 155 - 170.
4. Vanderwerf, E.A., Becker, B.L., Eijzenga, J. and Eijzenga, H. (2008) Nazca booby Sula granti and Brewster’s brown booby Sula leucogaster brewsteri in the Hawaiian Islands and Johnston and Palmyra atolls. Marine Ornithology, 36: 67 - 71.
5. Grace, J. and Anderson, D.J. (2009) Masked Booby (Sula dactylatra). In: Poole, A. (Ed) The Birds of North America. Cornell Lab of Ornithology, Ithaca. Available at:
   http://bna.birds.cornell.edu/bna/species/073
6. Horwell, D. and Oxford, P. (2005) Galápagos wildlife. Bradt Travel Guides, Chalfont St. Peter.
7. Morgan, S.M., Ashley-Ross, M.A. and Anderson, D.J. (2003) Foot-mediated incubation: Nazca booby (Sula granti) feet as surrogate brood patches. Physiological and Biochemical Zoology, 76: 360 - 366.
8. Humphries, C.A., Arevalo, V.D., Fischer, K.N. and Anderson, D.J. (2006) Contributions of marginal offspring to reproductive success of Nazca booby (Sula granti) parents: tests of multiple hypotheses. Oecologia, 147: 379 - 390.
9. Anderson, D.J., Porter, E.T. and Ferree, E.D. (2004) Non-breeding Nazca boobies (Sula granti) show social and sexual interest in chicks: Behavioural and ecological aspects. Behaviour, 141: 959 - 977.
10. ProAves (June, 2009)
    http://www.proaves.org/article.php?id_article=560