Blue-footed booby (Sula nebouxii)
|Size||Length: 76 - 84 cm (2)|
Wingspan: 152 - 158 cm (2) (3)
Male weight: 1.1 - 1.5 kg (4)
Female weight: 1.3 - 2.0 kg (4)
Classified as Least Concern (LC) on the IUCN Red List (1).
The blue-footed booby is a large and rather comical-looking seabird, instantly recognisable by its bright blue webbed feet. The head and neck are heavily streaked with brown and white, giving a distinctive ‘spiky’ appearance, while the wings and upperparts are dark brown, with some white barring or scaling on the back, and a large white patch on the upper back and on the rump. The underparts are white, and the tail is dark brown, with white central feathers. The wings are long and pointed (3) (5) (6) (7). The beak of the blue-footed booby is dark greenish-blue or grey, merging into the dark skin of the face and gular pouch, and the eye is a piercing yellow (5) (6) (7) (8). The call of the male blue-footed booby is a plaintive whistle, while the female uses a hoarse, grunting ark-ark-ark (5) (8).
The female blue-footed booby is similar in appearance to the male, but can be distinguished by the dark inner iris in the eye, giving the appearance of a larger pupil (2) (3) (5). The female is also larger than the male, but has a proportionately shorter tail (5). Immature birds are more uniform brown on the head, neck, upperparts and upper breast, with a white belly, duller legs, and brown or greyish eyes (2) (5) (6) (8). Two subspecies of blue-footed booby are usually recognised: Sula nebouxii nebouxii, and the larger and paler Sula nebouxii excisa (2) (5) (6).
The blue-footed booby occurs along the Pacific coast of the Americas, from California in the north, to northern Peru or sometimes northern Chile in the south, with breeding usually occurring from Mexico to Peru. S. n. excisa is found in the Galapagos Islands (2) (5) (6) (8).
The blue-footed booby is a coastal species, foraging in cool, offshore waters, and nesting on open ground on rocky coasts, cliffs or islands (2) (3) (6).
The name ‘booby’ comes from the Spanish word bobo, meaning ‘fool’ or ‘dunce’, referring to the clumsiness of boobies on land (9). However, in the air the blue-footed booby is a strong and agile flier (5) (8) (9), foraging by plunge-diving into water, often from a considerable height (3) (8) (9). A social species, it often forages in groups of up to 200 birds (2) (7) (8), mainly taking fish such as sardines, anchovies and mackerel, as well as some squid (2) (4) (5). It has also been reported to take flying-fish (Exocoetus) from the air (2) (3).
The blue-footed booby usually nests in colonies of up to several hundred, although pairs may also nest alone (5). Breeding may be seasonal in some areas, but occurs opportunistically in others (2). Boobies usually mate for life (9), and perform an elaborate and somewhat comical courtship display that involves the male ‘skypointing’ (pointing the head and beak upwards and spreading the wings), alternately lifting each blue foot, with the tail held cocked, and often emitting a whistling call. Both members of the pair may then skypoint, touch beaks, lift the feet, or pick up twigs or stones and place them on the ground (9) (10). The nest is built on bare ground, within a circle formed from accumulated guano (2) (3). One to three eggs are laid (2) (3), hatching after an incubation period of around 41 days (2). Interestingly, boobies does not have a brood patch, but incubate the eggs using heat supplied from a rich network of blood vessels in the webs of the feet (9). Unlike some other booby species, the blue-footed booby does not show obligate brood reduction (where one or more of the chicks are always lost) (2) (5), but if food becomes limiting the eldest chick may exclude younger chicks, which may then starve (5). Surviving chicks fledge after around 102 days, and are dependent on the adults for a further 56 days. Breeding may occur from two to three years old (2).
The blue-footed booby is not believed to be globally threatened (2) (11), and still has a large range and a large global population, which is thought to be stable (11). Little information is available on the potential threats to the blue-footed booby from human activities such as fishing, or from the effects of global warming on the marine ecosystem. However, in the Galapagos this charismatic species may be vulnerable to a number of threats facing the islands, including introduced predators, increasing tourism and urbanisation, unsustainable fishing, pollution, and habitat degradation (2) (12).
No specific conservation measures are known to be in place for the blue-footed booby throughout most of its range. However, it is protected in the Galapagos Islands (3), where its numbers, breeding success and population are regularly monitored (2), and where various conservation efforts are underway to protect the unique wildlife of these fascinating islands (12).
To find out more about the blue-footed booby, and about conservation in the Galapagos Islands, see:
The Cornell Lab of Ornithology:
Galapagos Conservation Trust:
Charles Darwin Foundation:
For more information on this and other bird species please see:
- Brood patch: an area of featherless skin on the underside of a bird during the nesting season. Well supplied with blood vessels, this patch of skin aids the transfer of heat to the eggs.
- Guano: accumulated droppings found where large colonies of animals such as seals, bats or birds occur; it is rich in plant nutrients.
- Gular pouch: a large distensible pouch below the beak of some birds.
- Incubate: to keep eggs warm so that development is possible.
- Incubation: the act of incubating eggs; that is, keeping them warm so that development is possible.
- 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.
IUCN Red List (June, 2009)
- del Hoyo, J., Elliott, A. and Sargatal, J. (1992) Handbook of the Birds of the World. Volume 1: Ostrich to Ducks. Lynx Edicions, Barcelona.
The Cornell Lab of Ornithology - All About Birds: Blue-footed Booby (June, 2009)
- Zavalaga, C.B., Benvenuti, S., Dall’Antonia, L. and Emslie, S.D. (2007) Diving behavior of the blue-footed boobies Sula nebouxii in northern Peru in relation to sex, body size and prey type. Mar. Ecol. Prog. Ser., 336: 291 - 303.
- Nelson, J.B. (2005) Pelicans, Cormorants, and their Relatives. The Pelecaniformes. Oxford University Press, Oxford.
- Blake, E.R. (1977) Manual of Neotropical Birds. Volume 1: Spheniscidae (Penguins) to Laridae (Gulls and Allies). University of Chicago Press, Chicago and London.
- Ridgely, R.S. and Gwynne, J.A. (1992) A Guide to the Birds of Panama: with Costa Rica, Nicaragua, and Honduras. Second Edition. Princeton University Press, Princeton, New Jersey.
- Hilty, S.L. and Brown, W.L. (1986) A Guide to the Birds of Colombia. Princeton University Press, Princeton, New Jersey.
- Burton, M. and Burton, R. (2002) International Wildlife Encyclopedia. Third Edition. Marshall Cavendish, New York.
- Jackson, M.H. (1993) Galápagos: A Natural History. University of Calgary Press, Calgary.
BirdLife International (June, 2009)
UNEP-WCMC: Galápagos Islands National Park and Marine Reserve, Ecuador (June, 2009)