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Fregata magnificensmagnificent frigatebird

By Martha Calcutt

Geographic Range

Magnificent frigatebirds live along American, tropical coastlines. They breed as far north as 25 degrees north latitude in Mexico and Florida and as far south 27 degrees south latitude in Brazil. They are especially common in southern Florida, the Gulf Coast, the Caribbean islands and the west coast of Mexico. (Diamond and Schreiber, 2002; Stefferud, 1966)

Habitat

Magnificent frigatebirds usually build their nests out of twigs on or around low-lying vegetation. Males gather twigs and other nest building materials while females remain at the males' display site and build the nest there. Nests are primarily constructed at ground level, but sometimes in trees as well. Nests are flat or slightly hollow with a diameter of 25 - 35 cm. They are usually fully exposed to the sun for the birds' sunning habits. A colony of magnificent frigatebirds can occupy about 500 m of shoreline with a total area of about 22,500 m squared. A colony with about 2500 pairs of birds in Barbuda, a small island in the Caribbean, is the largest known colony. (Diamond and Schreiber, 2002; Diamond, 1973)

Physical Description

Male magnificent frigatebirds are entirely black except for brown inner secondaries on the upper wing and the presence of a red inflatable throat pouch called a gular sac. They also have faint purple gloss on the head and green on the neck, scapulars, and upper wing. Their legs and feet appear back or grayish. Females are also entirely black with a white chest and white and tan markings on the wings. Their legs and feet are flesh-colored or pink, and they lack a gular sac. Females are, in general, 15% larger than males. Immature magnificent frigatebirds have a white head and chest while the rest of the body is black. Their legs, feet, and bill are light-bluish gray.

Their large heads, long, pointed, narrow wings, and forked tails make them easy to distinguish even from a distance. They are most often seen soaring along coastlines at higher altitudes and their silhouette is readily recognizable. They are also recognizable by their large size and long, hooked bill. They have short legs and small feet not well-suited to walking or swimming. (Audubon, 1950; Diamond and Schreiber, 2002; Orr, 1992; "USGS", 1995)

  • Sexual Dimorphism
  • female larger
  • sexes colored or patterned differently
  • male more colorful
  • ornamentation
  • Range mass
    1360 to 1815 g
    47.93 to 63.96 oz
  • Range length
    100 to 230 cm
    39.37 to 90.55 in
  • Range wingspan
    90 to 230 cm
    35.43 to 90.55 in

Reproduction

During the breeding season, male magnificent frigatebirds congregate at male display sites. They inflate their large, red, gular sacs. These sacs, while inflated, can get so large that they obscure the bird's head. Males rapidly vibrate their wings and sit back on their tails. They stretch their wings out and throw their heads back for maximum display of the gular sac. Females then inspect the males. As females attempt to find a preferred mate, males twist and bend to make their gular sac look as large a possible, they also make a loud, drumming noise during this display. Magnificent frigatebirds form monogamous pairs each breeding season once females have selected mates. However, they rarely maintain the same partner from season to season. (Diamond and Schreiber, 2002; Diamond, 1973; Madsen, et al., 2004)

Female magnificent frigatebirds lay a single egg three to four weeks after the beginning of breeding season. The incubation period for this species is not recorded, but has been estimated at 50 days. Because female parent involvement continues for much longer than male parental involvement, females only mate every other year. Males rarely care for their young longer than six months and breed annually. Juveniles near mature mass before fledging. Age of sexual maturity is not known but none breed until plumage is in mature phase. (Diamond and Schreiber, 2002; Diamond, 1973; Trivelpiece and Ferraris, 1987)

  • Breeding interval
    Female magnificent frigatebirds breed biannually, males attempt to breed annually.
  • Breeding season
    Magnificent frigatebirds lay their eggs between mid-December and early April.
  • Range eggs per season
    1 (high)
  • Average eggs per season
    1
  • Average eggs per season
    1
    AnAge
  • Average time to hatching
    50 days
  • Average time to hatching
    50 days
    AnAge
  • Range fledging age
    120 to 200 days
  • Range time to independence
    21 to 24 months

A magnificent frigatebird's egg is almost never exposed, being nearly continuously monitored by a parent. Hatchlings are altrical and are usually protected beneath a brooding parent. After about three weeks they are left alone in the nest for approximately half of daylight hours as parent birds search for food. Both parents contribute to provisioning hatchlings, but males contribute less than 40% of feeding. Around the sixth week the hatchling is substantially developed and can defend itself. At about the eleventh week, the male parent abandons the nest, leaving remaining parenting to the female. Females then compensate by nearly doubling the food provided for the hatchling. Females continue to feed hatchlings until they fledge and leave the nest. Often involvement continues after fledging, up to approximately four months. (Diamond and Schreiber, 2002; Diamond, 1973; Elorduy, 1995; Osorno and Székely, 2004; Osorno, 1999)

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

Lifespan/Longevity

While there is little data on magnificent frigatebird lifespan, it is estimated at 30 years. Besides natural death, mortality is occasionally caused by destructive hurricanes and man-made interferences in colonies. (Diamond and Schreiber, 2002)

Behavior

Magnificent frigatebirds are birds of the open ocean. Although their nests are on coastal areas, these birds are in flight for a majority of the time. Often they fly long distances over open water far from land. Their wings are so large that flying is nearly effortless. They take advantage of updrafts and can glide for long distances without beating their wings. They use their long, forked tails for maneuvering. They are one of the only birds with the ability to ride out a hurricane's strong winds. While usually solitary in flight, they do nest in colonies with numerous other pairs. While feeding, they can be extremely aggressive towards other animals. They are otherwise docile and while on land will often allow humans to come very close and even touch them. While their legs are not well-suited to walking, their strong, webbed toes allow them to perch when not in flight. Aggression, while rare, is usually in the form of bill snapping and jabbing at other birds when competing for perch sights. They do not defend territory beyond their small nest areas. Fledglings' often interact in playful ways. (Berridge, 1934; Diamond and Schreiber, 2002; Peterson and The editors of LIFE, 1963)

Home Range

There is no information available on the home ranges of magnificent frigatebirds.

Communication and Perception

Magnificent frigatebirds are usually silent, but they do vocalize when approaching a colony, when begging for food (hatchlings), and during mating displays. Little is known about communication among frigatebirds. (Diamond and Schreiber, 2002; Diamond, 1973)

Food Habits

Magnificent frigatebirds eat mainly fish, as well as squid, jellyfish, and crustaceans. However, their diet can greatly vary due to food availability and preferred hunting technique. The three main hunting techniques are dipping, kleptoparasitism, and opportunistic feeding. When dipping, these birds gracefully glide just above the surface of the water and skim the surface with their beak to catch fish. However, they are only able to dip about 15 cm deep to avoid getting their feathers wet. Kleptoparasitism, the stealing of another animal’s food, is how this species gets one of their nicknames, "Man-'o-War". They chase other birds, particularly gulls, gannets, terns, and boobies. This chase continues until the victim is forced to disgorge their food. Magnificent frigatebirds then catch the disgorged food in mid air. They may also catch the other bird by the tail feathers and shake it until they release their food. Opportunistic feeding involves eating garbage, young turtles at hatching, and otherwise taking advantage of all available food sources. Magnificent frigatebirds eat fish scraps discarded by boats, offal (discarded parts of animals unfit for consumption) from slaughterhouses, and other garbage. Occasionally they steal food from the hands of humans. Females consume more than males because of their larger size and greater contribution to the feeding of hatchlings. (Colixto-Albarrán and Orsorno, 2000; Diamond and Schreiber, 2002; Diamond, 1973; Elphick, 2004; Osorno, et al., 1992; Peterson and The editors of LIFE, 1963)

  • Animal Foods
  • fish
  • mollusks
  • aquatic crustaceans
  • cnidarians

Predation

There are no known birds that prey on magnificent frigatebirds. Mammals may sometimes take eggs and nestlings. However, magnificent frigatebirds closely monitor their eggs and hatchlings until they are fairly able to defend themselves and breeding occurs in colonies, where many eyes can keep watch for predators. (Diamond and Schreiber, 2002)

Ecosystem Roles

Magnificent frigatebird feeding habits affect their fish prey, especially flying fish (Exocoetidae), as well as some squid and crustaceans. Other birds like pelicans, gulls, gannets, terns, and boobies are affected by magnificent frigatebird kleptoparasitism. Magnificent frigatebirds are often found near groups of dolphins, tuna, or other predatory fish that drive much of their prey to the surface of the water. This makes magnificent frigatebirds more successful when using a dipping hunting technique. (Heiling, et al., 2003; Osorno, et al., 1992)

Economic Importance for Humans: Positive

Magnificent frigatebirds are beautiful and may attract ecotourism. They are also important members of the healthy ecosystems they inhabit.

Economic Importance for Humans: Negative

There are no known negative impacts of magnificent frigatebirds on humans.

Conservation Status

There are an estimated 50,000 to 71,000 breeding pairs of magnificent frigatebirds. Their numbers are apparently declining, due to human disturbances to nesting areas. There is a need for more research and protection plans in order to ensure that magnificent frigatebird populations remain stable. Regulations have been proposed to the Government of Antigua and Barbuda, but there is no current legal protection for this species. (Diamond and Schreiber, 2002)

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Martha Calcutt (author), University of Notre Dame, Karen Powers (editor, instructor), Radford University.

Glossary

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

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.

arboreal

Referring to an animal that lives in trees; tree-climbing.

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.

estuarine

an area where a freshwater river meets the ocean and tidal influences result in fluctuations in salinity.

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).

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.

oviparous

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

piscivore

an animal that mainly eats fish

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

sexual ornamentation

one of the sexes (usually males) has special physical structures used in courting the other sex or fighting the same sex. For example: antlers, elongated tails, special spurs.

solitary

lives alone

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

References

UC Regents. 1995. "USGS" (On-line). Fregata magnificens. Accessed April 11, 2006 at http://pick4.pick.uga.edu/mp/20q?search=Fregata+magnificens&guide=Birds&cl=US/MA&flags=not_no:.

Audubon, J. 1950. Audubon's Birds of America (popular edition). New York: The Macmillan Company.

Berridge, W. 1934. All About Birds. New York: Robert M McBride and Company.

Colixto-Albarrán, I., J. Orsorno. 2000. The Diet of the Magnificent Firgatebird During Chick Rearing. The Condor, 102/3: 569-576. Accessed April 11, 2006 at http://www.bioone.org.lib-proxy.nd.edu/perlserv/?request=get-document&issn=0010-5422&volume=102&page=569#page_top.

Diamond, A. 1973. Notes on the Breeding Biology and Behavior of the Magnificent Frigatebird. The Condor, 75: 200-209. Accessed April 11, 2006 at http://www.jstor.org/view/00105422/ap040430/04a00100/0?frame=frame&userID=814a704a@nd.edu/01cce4403100509b82e&dpi=3&config=jstor.

Diamond, A., E. Schreiber. 2002. Magnificent Frigatebird. The Birds of North America, 601: 1-24.

Elorduy, J. 1995. Hatching, growth, and mortality of Magnificent Frigatebird chicks in Southern Baja California. Wilson Bulletin, 107/2: 328. Accessed April 11, 2006 at http://infotrac.galegroup.com.lib-proxy.nd.edu/itw/infomark/428/838/85516356w2/purl=rc1_EAIM_0_A17224448&dyn=5!xrn_1_0_A17224448?sw_aep=nd_ref.

Elphick, J. 2004. Birds: The Art of Ornithology. New York: Rizzoli.

Heiling, A., M. Herberstein, L. Chittka. 2003. Frigatebirds ride high in thermals. Nature, 421: 333-334. Accessed April 11, 2006 at www.nature.com/nature.

Madsen, V., T. Balsby, T. Debelsteen, J. Osorno. 2004. Bimodal Signaling of a Sexually Selected Trait: Gular Pouch Drumming in the Magnificent Frigatebird. The Condor, 106/1: 156-160. Accessed April 11, 2006 at http://www.bioone.org.lib-proxy.nd.edu/perlserv/?request=get-document&issn=0010-5422&volume=106&page=156.

Orr, O. 1992. Saving American Birds. Florida: University Press of Florida.

Osorno, J., R. Torres, C. Macias Garcia. 1992. Kleptoparasitic Behavior of the Magnificent Frigatebird: Sex and Bias and Success. The Condor, 94: 692-698. Accessed April 11, 2006 at http://www.jstor.org.lib-proxy.nd.edu/view/00105422/ap040506/04a00150/0?frame=frame&userID=814afac5@nd.edu/01cce4401e00509e6fe&dpi=3&config=jstor.

Osorno, J. 1999. Offspring desertion in the Magnificent Frigatebird: are males facing a trade-off between current and future reproduction?. Journal of Avian Biology, 30: 335-341.

Osorno, J., T. Székely. 2004. Sexual conflict and parental care in magnificent frigatebirds: full compensation by deserted females. Animal Behaviour, 68/2: 337-342. Accessed April 11, 2006 at http://www.sciencedirect.com.lib-proxy.nd.edu/science?_ob=ArticleURL&_udi=B6W9W-4CPVK9Y-4&_coverDate=08%2F31%2F2004&_alid=389439147&_rdoc=1&_fmt=&_orig=search&_qd=1&_cdi=6693&_sort=d&view=c&_acct=C000022718&_version=1&_urlVersion=0&_userid=489835&md5=59d9f51c4becb9aa162484889444003b.

Peterson, R., The editors of LIFE. 1963. The Birds. New York: Time Incorporated.

Stefferud, A. 1966. Birds In Our Lives. Washington: United States Government Printing Office.

Trivelpiece, W., J. Ferraris. 1987. Notes ont eh behavioural ecology of the magnificent frigatebird Fregata magnificens. Ibis, 129/2: 168-174. Accessed April 11, 2006 at http://www.csa.com/partners/viewrecord.php?requester=gs&collection=ENV&recid=1646941&q=&uid=&setcookie=yes.

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