Sulaboobies

Diversity

There are six species of birds known as boobies in the genus Sula. These medium to large seabirds are found in marine and coastal habitats including islands, coastal areas, and temperate, pan-tropical oceans (Lee and Haney, 1984). Boobies vary in size (1000 to 2500 grams), but generally have long wings, a wedge-shaped tail, short and far-set legs, totipalmate feet (four toes with webbing), and a conical bill with a decurved tip (Diaz, Alfredo and Salazar Gomez, 2011). The species within Sula exhibit sexual dimorphism with females often larger than males (Cornell University, 2015). Although physically similar, different species of boobies exhibit unique behaviors and other differences in their ecology. Plumage and bill color varies between species, with some having brightly-colored feet used for mating rituals. Boobies feed primarily on shoaling fish and use a streamlined, powerful, headfirst dive from up to 25 meters in the air into the water to catch prey (National Geographic, 2018). They fold their long wings back to further streamline the body for a more efficient headfirst dive (Diaz, Alfredo and Salazar Gomez, 2011). Species in Sula form pairs during breeding season through ritualized mating performances that show off their webbed feet, although infidelity frequently occurs throughout the large nesting colonies that are formed (Nelson, 1978). ("Blue-footed Booby", 2015; Diaz, et al., 2011; Lee and Haney, 1984; "Red-footed Booby", 2018; Nelson, 1978)

Geographic Range

Sula species live in temperate, pantropical waters across the world. Although nonmigratory, boobies are widely distributed across marine and coastal areas in the Gulf of California, throughout the Caribbean Sea, along the Pacific coast to northern Peru, and west to the Galapagos Islands (Nelson, 1978). The species of Sula are also found on small oceanic islands surrounded by temperate waters in seas north of Australia and throughout the Indian, Pacific, and Atlantic Oceans (Lee and Haney, 1984). On rare occasions, blue-footed boobies (Sula nebouxii), masked boobies (Sula dactylatra), brown boobies (Sula leucogaster), and red-footed boobies (Sula sula) have been observed off the Pacific and Atlantic coasts of the United States (Florida and California) (Sibley, 2014). (Diaz, et al., 2011; Lee and Haney, 1984; Nelson, 1978; Sibley, 2014)

Habitat

The majority of Sula species are solitary marine foragers that return from sea and roost on coral atolls, volcanic islands, coasts, and oceanic islands (Nelson, 1978). Blue-footed boobies (Sula nebouxii) and red-footed boobies (Sula sula) are occasionally seen foraging in small groups off of rocky islets and shorelines near roosts (Cornell University, 2015). Each species has a unique habitat preference for nesting. The majority of species, excluding red-footed boobies, nest on open, minimally shaded ground. Red-footed boobies are the only arboreal nesters (Nelson, 1969). Different Sula species can be found roosting in the same areas although territorial aggression between different species occurs, resulting in differences in nest site selection. For example, Blue-footed Boobies in the Galapagos Islands nest at coastal sites if Nazca boobies (Sula granti) are not present, but blue-footed boobies move further away from ideal nesting habitat when Nazca boobies are present (Townsend et al, 2002). ("Blue-footed Booby", 2015; Nelson, 1969; Nelson, 1978; Townsend, et al., 2002)

Physical Description

Sula species are medium to large birds (800 to 2400 g; 70 to 85 cm long) with wingspans up to five feet long (37.4 to 170 cm) (Nelson, 1978). Boobies are sexually dimorphic, with females generally being larger and weighing more than males. Only one species, the red-footed booby (Sula sula) exhibits color polymorphism, with up to five different color morphs (brown, white, black-tailed white, white-tailed brown, and white-headed brown) (Sibley, 2014). Sula species have a variety of plumage colors ranging between white, brown and black. Juveniles tend to have darker brown and black plumage but, as hatchlings they are covered in white down feathers. The often colored (red, blue, gray, yellow, black) totipalmate feet (four webbed toes) of Sula species are set far back on the body. Boobies have desmognathous palates with no exposed outside nares, and nasal grooves running down the stout, conical bill (Nelson, 1978). Adult boobies have bare facial and gular skin (Sibley, 2014). The featherless skin, bill, and feet are colored differently based on the species, which can be red, blue, gray, yellow, or black (Sibley, 2014). Boobies have binocular vision because each eye is situated on either side of the bill. The largest Sula species is the masked booby (Sula dactylatra), with males ranging between 1220 and 2211 grams and females ranging between 1470 and 2400 grams ("Sula dactylatra (Masked Booby)", 2016). Red-footed boobies (Sula sula) are the smallest Sula species, with males between 800 and 1160 grams and females between 850 and 1210 grams (Sibley, 2014 and Nelson, 1978). Boobies are most closely related to gannets (Morus), but have key differences between them. Gannets are monomorphic in size, are migratory, and have feathers extending forward of the eyes, while boobies are sexually dimorphic, sedentary, and have bare facial skin forward from the eyes. ("Sula dactylatra (Masked Booby)", 2016; Nelson, 1978; Sibley, 2014)

  • Sexual Dimorphism
  • female larger

Reproduction

Sula species are monogamous, but occasionally partake in infidelity when their mate is out foraging for food on the ocean (Nelson, 1978). As breeding season approaches, male boobies defend a territory and once a female pairs with a male, they jointly choose a breeding site to defend within the male’s territory (Nelson, 1978). Sula males and females perform a complex display to find, attract, and bond with a mate. Sula courtship displays involve exaggerated raising and flaunting of feet to their partner called “parading” (Nelson, 1978). To females, the color of the feet is a good indicator of the male’s physical and reproductive health. The brighter the feet are, the healthier the mate is. Breeding pairs typically practice this courtship display more than once over the breeding season to protect nesting territory and solidify their bond (Diaz, Alfredo and Salazar Gomez, 2011). Both female and male boobies practice extra-pair copulation during fertile periods. (Diaz, et al., 2011; Nelson, 1978)

Boobies nest in colonies and their breeding season can last up to 40 weeks (Nelson, 1978). Breeding season is divided into four main stages: pre-laying, incubation, chick care and post breeding (Nelson, 1978). Pre-laying is comprised of defending nest territories and establishing adequate bonding pair relationships (Nelson, 1978). Clutch sizes range from 1 to 3 eggs (blue to white in color) (Nelson, 1978). Most boobies nest on the ground, excluding red-footed boobies, who nest in trees (Nelson, 1969). The incubation period lasts around 50 days, with both males and females alternating egg incubation (Nelson, 1978). Boobies do not have brooding patches and use their totipalmate feet to transfer heat to the eggs. g. Sula males that doubt the paternity of their egg are known to destroy all of the eggs in the nest (Diaz, Alfredo and Salazar Gomez, 2011).. g. Sula hatchlings are featherless and gradually gain white down feathers (Nelson, 1978). As juveniles, the plumage is dark brown to black (Nelson, 1978). Hatchlings are altricial and require male and female care for an average of 100 days, during which hatchlings are completely dependent on their parents for food and protection (Nelson, 1978). Both parents forage for food in the ocean and regurgitate semi-digested food into the hatchling’s mouth. Nestlings are vulnerable to predators like hawks and short-eared owls during the day when both parents are out foraging (Mellink, Dominguez and Luevano, 2000). In the Galapagos, adult Nazca boobies attack and injure blue-footed booby nestlings to prevent successful fledging (Townsend et al, 2002). (Diaz, et al., 2011; Mellink, et al., 2000; Nelson, 1969; Nelson, 1978; Townsend, et al., 2002)

Males and females take turns incubating the eggs by transferring heat from their totipalmate feet (Diaz, Alfredo, and Salazar Gomez, 2011). Each parent guards the nest through the night if the counterpart is out at sea foraging. Once the egg hatches, each parent forages for food for the nestlings (Nelson, 1978). The nestlings are under parental care for approximately 100 days, until they are mature enough to forage for themselves (Nelson, 1978). (Diaz, et al., 2011; Nelson, 1978)

  • Parental Investment
  • altricial
  • male parental care
  • female parental care
  • pre-fertilization
    • protecting
      • male
      • female
  • pre-hatching/birth
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-weaning/fledging
    • provisioning
      • male
      • female
    • protecting
      • male
      • female
  • pre-independence
    • provisioning
      • male
      • female
    • protecting
      • male
      • female

Lifespan/Longevity

The typical lifespan of boobies is 17 years to a maximum 30 years (Nelson, 1978). The oldest banded brown booby recorded was 27.2 years old (Longevity Records of North American Birds, 2017). Adult mortality rate for boobies is 5-10% (Nelson, 1978). Factors that limit their lifespan include predation on land and sea, pressures from commercial fishing, coastal development, and subsequent habitat destruction (National Geographic, 2018). ("Red-footed Booby", 2018; Nelson, 1978; "Longevity Records of North American Birds", 2017)

Behavior

Boobies are social species that live and breed in colonies. Boobies are piscivores that forage solitarily, in small groups, or in large groups, depending on the species. Sula can dive up to 25 meters deep in the ocean for fish (Cornell University, 2015). Boobies pair up during mating season and perform elaborate rituals showcasing the feet, jabbing bills, and nodding the head (Nelson, 1978). Males of Sula defend small nesting areas and are territorial during breeding season (Diaz, Alfredo and Salazar Gomez, 2011). Agonistic behavior occurs between blue-footed booby siblings (Diaz, Alfredo and Salazar Gomez, 2011). Larger offspring will peck their smaller siblings, causing parents to selectively feed the larger, more dominant (and healthy looking) offspring. This can lead to starvation and death of the smaller sibling (Diaz, Alfredo and Salazar Gomez, 2011). Boobies use calls and body language to communicate. ("Blue-footed Booby", 2015; Diaz, et al., 2011; Nelson, 1978)

Communication and Perception

Sula species are silent at sea. On breeding grounds, adult males whistle and bray, while females and juveniles vocalize with a deep, duck-like note (Diaz, Alfredo and Salazar Gomez, 2011). Potential mates communicate through elaborate courtship displays, characterized by sky-pointing with beaks, gazing, mutual jabbing, and parading feet (Nelson, 1978). Boobies exhibit aggressive behavior to establish their territory. This includes aerial attacks, wing-flailing, jabbing bill toward their opponent, and head bowing (Nelson, 1969). Sula species do not exhibit social or hierarchical ranking. (Diaz, et al., 2011; Nelson, 1969; Nelson, 1978)

  • Other Communication Modes
  • duets

Food Habits

Sula species are piscivores that feed on small, pelagic shoaling fishes like anchovies (Cetengraulis mysticetyus and Engraulis mordax), sardines (Sardinops sagax), mackerels, flying fish (Exocoetidae), and squid (Loliginidae) (Mellink, Dominguez and Luevano, 2000; and Diaz, Alfredo, and Salazar Gomez, 2011). (Diaz, et al., 2011; Mellink, et al., 2000)

Predation

Sula species are preyed on by owls (Strigiformes), condors (Cathartidae), sharks, rats, humans, cats, and gulls (Laridae) (Mellink, Dominguez and Luevano, 2000 and Nelson, 1978). (Mellink, et al., 2000; Nelson, 1978)

Ecosystem Roles

Sula species are prey to cats, rats, fish, and birds, and are predators to shoaling fish like mackerel, anchovies, flying fish, sardines, and squid (Mellink, Dominguez and Luevano, 2000). (Mellink, et al., 2000)

Economic Importance for Humans: Positive

Boobies are of economic importance to tourism industries around the globe. For example, blue-footed boobies frequent the Galapagos and are of interest to tourists. Tourists also visit red-footed boobies that nest on Caribbean islands. Scientists are interested in the ecology and ecosystem roles of boobies. These pelagic birds are indicator species of ocean and ecosystem health. Booby fecal matter, or guano, has historically been used as a crop fertilizer. The demand for guano has increased as a result of the price increase of synthetic fertilizers and upward trend favoring organic produce (Highfield, 2011). Guano is primarily collected on islands off the coast of Peru, and is shipped as far as Europe to fertilize different crops (Highfield, 2011). (Highfield, 2011)

Economic Importance for Humans: Negative

There are no known adverse effects of Sula on humans.

Conservation Status

Masked (Sula dactylatra), blue-footed (Sula nebouxii), brown (Sula leucogaster), and red-footed boobies (Sula sula) are protected species under the Migratory Bird Treaty Act ("Migratory Bird Treaty Act", 2013). The IUCN Red List classifies all species in Sula as species of least concern ("Sula dactylatra (Masked Booby)", 2016 and "Sula variegata (Peruvian Booby)", 2016). The population numbers of masked, brown, red-footed, and Nazca (Sula granti) boobies are decreasing according to the IUCN Red List. Abbott’s booby (Papasula abbotti), a species in the the sister genus of Sula, Papasula, is listed on CITES, but no Sula species are listed ("UNEP", 2018). Declines in populations are attributed to food scarcity caused by overfishing, and coastal habitat fragmentation and loss (National Geographic, 2018). ("Migratory Bird Treaty Act", 2013; "Sula dactylatra (Masked Booby)", 2016; "Sula variegata (Peruvian Booby)", 2016; "UNEP", 2018; "Red-footed Booby", 2018)

  • IUCN Red List [Link]
    Not Evaluated

Other Comments

Species in Sula are thought to get their common name, “booby” from the Spanish word “bobo”. The term translates to “stupid” in English and is thought to be representative of the clumsy, goofy walk the booby exhibits on land (National Geographic, 2018). ("Red-footed Booby", 2018)

Contributors

Makenna Spencer (author), Colorado State University, Tanya Dewey (editor), University of Michigan-Ann Arbor.

Glossary

Australian

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

World Map

Nearctic

living in the Nearctic biogeographic province, the northern part of the New World. This includes Greenland, the Canadian Arctic islands, and all of the North American as far south as the highlands of central Mexico.

World Map

Neotropical

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

World Map

Pacific Ocean

body of water between the southern ocean (above 60 degrees south latitude), Australia, Asia, and the western hemisphere. This is the world's largest ocean, covering about 28% of the world's surface.

World Map

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.
duets

to jointly display, usually with sounds in a highly coordinated fashion, at the same time as one other individual of the same species, often a mate

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.

female parental care

parental care is carried out by females

fertilization

union of egg and spermatozoan

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).

male parental care

parental care is carried out by males

monogamous

Having one mate at a time.

motile

having the capacity to move from one place to another.

natatorial

specialized for swimming

native range

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

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.

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

polymorphic

"many forms." A species is polymorphic if its individuals can be divided into two or more easily recognized groups, based on structure, color, or other similar characteristics. The term only applies when the distinct groups can be found in the same area; graded or clinal variation throughout the range of a species (e.g. a north-to-south decrease in size) is not polymorphism. Polymorphic characteristics may be inherited because the differences have a genetic basis, or they may be the result of environmental influences. We do not consider sexual differences (i.e. sexual dimorphism), seasonal changes (e.g. change in fur color), or age-related changes to be polymorphic. Polymorphism in a local population can be an adaptation to prevent density-dependent predation, where predators preferentially prey on the most common morph.

saltwater or marine

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

seasonal breeding

breeding is confined to a particular season

sedentary

remains in the same area

sexual

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

tactile

uses touch to communicate

temperate

that region of the Earth between 23.5 degrees North and 60 degrees North (between the Tropic of Cancer and the Arctic Circle) and between 23.5 degrees South and 60 degrees South (between the Tropic of Capricorn and the Antarctic Circle).

territorial

defends an area within the home range, occupied by a single animals or group of animals of the same species and held through overt defense, display, or advertisement

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

References

Cornell University. 2015. "Blue-footed Booby" (On-line). The Cornell Lab of Ornithology All About Birds. Accessed January 31, 2018 at https://www.allaboutbirds.org/guide/Blue-footed_Booby/id.

USGS. 2017. "Longevity Records of North American Birds" (On-line). Accessed February 26, 2018 at https://www.pwrc.usgs.gov/bbl/longevity/Longevity_main.cfm.

2013. "Migratory Bird Treaty Act" (On-line). U.S. Fish and Wildlife Service. Accessed February 28, 2018 at https://www.fws.gov/birds/management/managed-species/migratory-bird-treaty-act-protected-species.php.

National Geographic. 2018. "Red-footed Booby" (On-line). Accessed February 26, 2018 at https://www.nationalgeographic.com/animals/birds/r/red-footed-booby/.

2017. "Sula Brisson, 1760" (On-line). Integrated Taxonomic Information System (ITIS). Accessed February 11, 2018 at https://www.itis.gov/servlet/SingleRpt/SingleRpt?search_topic=TSN&anchorLocation=SubordinateTaxa&credibilitySort=Subordinate%20Taxa&rankName=Subspecies&search_value=174697&print_version=SCR&source=from_print#SubordinateTaxa.

2016. "Sula dactylatra (Masked Booby)" (On-line). The IUCN Red List of Endangered Species. Accessed January 31, 2018 at http://www.iucnredlist.org/details/22736173/0.

2016. "Sula variegata (Peruvian Booby)" (On-line). The IUCN Red List of Endangered Species. Accessed January 31, 2018 at http://www.iucnredlist.org/details/22696686/0.

2018. "UNEP" (On-line). The Species+ Website. Accessed February 28, 2018 at https://speciesplus.net/#/taxon_concepts/6600/references.

Chaves-Campos, J., J. Torres. 2002. Distribution of Nests of the Brown Booby (Sula Leucogaster) in Relation to the Inclination of Terrain. Ornitologia Neotropical, 13: 205-208. Accessed January 31, 2018 at http://www.avibirds.com/pdf/B/Bruine%20Gent5.pdf.

Diaz, H., J. Alfredo, E. Salazar Gomez. 2011. "Neotropical Birds Online" (On-line). Blue-footed Booby (Sula nebouxii). Accessed February 11, 2018 at https://neotropical.birds.cornell.edu/Species-Account/nb/species/bfoboo/overview.

Friesen, V., D. Anderson. 1997. Phylogeny and Evolution of the Sulidae (Aves: Pelecaniformes): A Test of Alternative Modes of Speciation. Elsevier, Volume 7, Issue 2: 252-260. Accessed January 31, 2018 at https://www-sciencedirect-com.ezproxy2.library.colostate.edu/science/article/pii/S1055790396903978?_rdoc=1&_fmt=high&_origin=gateway&_docanchor=&md5=b8429449ccfc9c30159a5f9aeaa92ffb&ccp=y.

Highfield, R. 2011. The New Guano Era. New Scientist, Vol. 212 Issue 2842: 26-27.

Lee, D., J. Haney. 1984. The Genus Sula in the Carolinas: An Overview of the Phenology and Distribution of Gannets and Boobies in the South Atlantic Bight. Chat, Vol. 41, No. 2: 29-45. Accessed January 31, 2018 at https://www.carolinabirdclub.org/chat/issues/1984/v48n2sula.pdf.

Mellink, E., J. Dominguez, J. Luevano. 2000. Diet of Eastern Pacific Brown Boobies Sula Leucogaster Brewsteri on Isla San Jorge, North-eastern Gulf of California, and an April Comparison with Diets in the Middle Gulf of California. Marine Ornithology, 29: 29-38. Accessed March 01, 2018 at http://citeseerx.ist.psu.edu/viewdoc/download?doi=10.1.1.669.9553&rep=rep1&type=pdf.

Nelson, B. 1978. The Sulidae: Gannets and Boobies. Aberdeen, UK: University of Aberdeen.

Nelson, J. 1969. The Breeding Ecology of the Red-footed Booby in the Galapagos. Journal of Animal Ecology, Vol. 38, No. 1: 181-198. Accessed January 31, 2018 at http://www.jstor.org.ezproxy2.library.colostate.edu/stable/2745?sid=primo&origin=crossref&seq=1#page_scan_tab_contents.

Sibley, D. 2014. The Sibley Guide to Birds 2nd Edition. New York: Alfred A. Knopf.

Townsend, H., K. Huyvaert, P. Hodum, D. Anderson. 2002. Nesting Distributions of Galápagos Boobies (Aves: Sulidae): An Apparent Case of Amensalism. Oecologica, Vol. 132, No. 3: 419-427. Accessed January 31, 2018 at http://www.jstor.org.ezproxy2.library.colostate.edu/stable/4223357?seq=1#page_scan_tab_contents.

Weimerskirch, H., S. Shaffer, Y. Tremblay, D. Costa, H. Gadenne, A. Kato, Y. Ropert-Coudert, K. Sato, D. Aurioles. 2009. Species- and sex-specific differences in foraging behaviour and foraging zones in blue-footed and brown boobies in the Gulf of California. Marine Ecology Process Series, Volume 391: 267-278. Accessed January 31, 2018 at http://www.jstor.org/stable/24873671.