Fregata andrewsi

Geographic Range

Christmas Island frigatebirds gets their name from the fact that they breed exclusively on Christmas Island, an island off the northwestern coast of Australia in the Indian Ocean. When not breeding, Christmas Island frigatebird range widely throughout Southeast Asia and the Indian Ocean, and are occasionally spotted near Sumatra, Java, Bali, Borneo, the Andaman Islands, and the Keeling Islands.

• Biogeographic Regions
• oriental oriental
  • native native
• australian australian
  • native native
• indian ocean
  • native native

Habitat

Christmas Island frigatebirds can be found in the tropical and subtropical waters of the Indian Ocean. Most of their time is spent at sea, the minimal time that is spent on land is for roosting and breeding. This species will roost communally and alongside other frigatebird species as well. Roosting and breeding sites are preferably high, as Christmas Island frigatebirds experience great difficulty taking of from perches less than 3 meters in height. They breed exclusively in the low dry forest of Christmas Island. This species prefers warmer, low salinity waters.

• Habitat Regions
• tropical tropical
• terrestrial terrestrial
• saltwater or marine saltwater or marine

• Terrestrial Biomes
• forest forest

• Aquatic Biomes
• pelagic pelagic
• coastal coastal

Physical Description

Christmas Island frigatebirds are large black sea birds with deeply forked tails and long hooked bills. Both sexes share a distinct white belly patch and pale bars on the upperwing. Females are larger than their male counterparts, with weights of 1550 g and 1400 g respectively. Males have a red gular pouch and the bill is dark grey. Females have a black throat and a pink bill. Females have a white collar and the belly patch extends onto the breast as well as the the axillaries as a spur. Juveniles have a distinct blue bill as well as a pale yellow head, the body is mostly brown with a blackish tail.

• Other Physical Features
• endothermic endothermic
• homoiothermic
• bilateral symmetry bilateral symmetry

• Sexual Dimorphism
• female larger
• sexes colored or patterned differently

Reproduction

Generally Christmas Island frigatebirds do not mate with partners from previous years; each season new mates are chosen as well as new nesting sites. In late December males select display sites, where they inflate their bright red gular pouch to attract females. Pairs are usually formed by the end February. The nest is then built at the display site. Christmas Island frigatebirds are colonial nesters and there are only 3 known colonies on the island, Golf Course, Dyers, and Cemetery. Christmas Island frigatebirds seem to be more selective in their nest sites than the other members of the genus Fregata . They prefer to nest in sites sheltered from high winds to ensure safe landings. Nest sites of Christmas Island frigatebirds are situated under the top branches of a chosen tree. This species is highly selective in the choice of tree species used for nesting, studies of the golf course colony have shown that Terminalia catappa and Celtis timorensis are the preferred species of nesting tree comprising 65.5% of the trees chosen. Nesting also occurs in some species of Ficus , but is less common. It is also noted that all of these tree species occur throughout the island, yet breeding is restricted to the 3 main colonies.

• Mating System
• monogamous monogamous

It takes over 40 days for a pair to incubate a single egg. The young generally hatch anywhere from mid-April to late-June. The offspring are very slow growing but seem to grow quicker than the young of other frigatebird species. It takes fifteen months to raise one chick, so breeding occurs only every 2 years, though it is not known whether both parents are required for the entire time. Males may attempt to mate every year.

• Key Reproductive Features
• iteroparous iteroparous
• seasonal breeding seasonal breeding
• gonochoric/gonochoristic/dioecious (sexes separate)
• sexual sexual
• oviparous oviparous

Fifteen months are needed for a pair to raise one young to independence. Both parents help in incubating the egg and feeding of the chick when hatched. Generally the older juveniles are fed by the female parent more frequenty than the male, although there have been observations of males feeding free-flying offspring at least 8 months old. About 15 to 20% the eggs that are laid fledge young. Some groups are able to raise 60% of nestlings successfully to fledging. It is estimated that a breeding pair takes twenty to twenty five years of breeding attempts, or more, to replace themselves.

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

Lifespan/Longevity

The mortality rate among Adult Christmas Island frigatebirds is 4% yearly, giving them an average lifespan of 25.6 years, it is speculated that they may live to reach ages of 40 to 45 years.

Behavior

Christmas Island frigatebirds are accomplished fliers, spending days out at sea on the wing. They are able to soar to impressive heights. They prefer to forage in warm, low-salinity waters. Christmas Island frigatebirds are solitary when foraging and live in colonies for breeding. They are active during the day.

• Key Behaviors
• flies
• diurnal diurnal
• motile motile
• nomadic nomadic
• solitary solitary
• colonial colonial

Home Range

It is thought that young Christmas Island frigatebirds are largely nomadic until they mature, as adults are generally not seen far from Christmas Island. Vagrants have been spotted near Java, Sumatra, Borneo, Bali, the Keeling Islands, Andaman Island and the Nicobar Islands of India.

Communication and Perception

Christmas Island frigatebirds use visual cues for mating, as when the males inflate their red gular pouches to attract females. They also use a variety of vocalizations to communicate in breeding colonies. Males and females distinctive vocalizations to communicate with each other and with their offspring.

• Communication Channels
• visual visual
• acoustic acoustic

• Perception Channels
• visual visual
• tactile tactile
• acoustic acoustic
• chemical chemical

Food Habits

Christmas Island frigatebirds are strictly surface feeders. They are largely piscivorious, feeding on flying fish, jellyfish, squid, large plankton, and fishery by-catch and offal. Being strictly surface skimmers, they generally only immerse their bill but sometimes they do immerse their entire head. They have been known to take eggs from other nests and prey on the young of other frigatebirds. They are sometimes called 'pirate birds' in reference to their habit of harassing other seabirds into releasing or regurgitating their prey, which they then take.

• Primary Diet
• carnivore carnivore
  • piscivore piscivore
  • molluscivore molluscivore
  • eats other marine invertebrates

• Animal Foods
• birds
• fish
• eggs
• mollusks
• aquatic crustaceans
• cnidarians
• zooplankton zooplankton

Predation

Other Christmas Island frigatebirds may prey on eggs and nestlings. Otherwise, there are few natural predators of frigatebirds. Nesting colonies are in isolated and inaccessible areas and are protected by the nesting birds.

Ecosystem Roles

Christmas Island frigatebirds are important predators of marine vertebrates and invertebrates where they occur.

Economic Importance for Humans: Positive

The many endemic species of birds found on Christmas Island draws eco-tourist groups of bird watchers. As of 2004 there is a rainforest rehabilitation program and a proposed frigatebird monitoring program that has the potential to provide more employment opportunities on the island.

• Positive Impacts
• ecotourism ecotourism
• research and education

Economic Importance for Humans: Negative

There are no known adverse effects of Christmas Island frigatebirds on humans.

Conservation Status

As of 1985 the breeding population of Christmas Island frigatebirds was censused at 1,620 pairs and in 2003 breeding pair numbers were estimated to be 1,171 (+/- 58). Other estimations of 4,500 for the entire population have been made, although difficulty in distinguishing immature Fregata andrewsi from other species of Fregata may make non-breeding population estimates inaccurate. Along with the population estimates done in 1985, estimations of nest numbers were also done, with 100 nests at the Dryers colony, 370 at the Cemetery colony and 850 at the Golf Course colony. Numbers have since decreased at Dryers to 30 nests. As of 1987 there were 4 known colonies, the 3 previously mentioned and the fourth being the Flying Fish Cove colony but in 2003 only 2 nests were present.

One of the main threats to the success of Christmas Island frigatebirds is the yellow crazy ant ( Anoplolepis gracilipes ). These ants form super-colonies that can stress trees to such an extent that they die, making the preferred nesting sites of Christmas Island frigatebirds unavailable. It is speculated that higher incidences of death from groundings occurs when the birds are grounded in these super-colonies. Due to its limited breeding range and preferred nesting sites, population numbers of Christmas Island frigatebirds are very sensitive to any changes in tree numbers.

Christmas Island frigatebirds are considered critically endangered by the IUCN and are on the CITES Appendix I.

Additional Links

Encyclopedia of Life

Contributors

Tanya Dewey (editor), Animal Diversity Web.

Andrew Jasonowicz (author), Northern Michigan University, Alec R. Lindsay (editor, instructor), Northern Michigan University.

References

Benstead, P., R. McClellan. 2007. "Christmas Frigatebird - BirdLife Species Factsheet" (On-line). Accessed April 18, 2008 at http://www.birdlife.org/datazone/species/index.html?action=SpcHTMDetails.asp&sid=3847&m=0 .

Fairbairn, J., R. Shine. 1993. Patterns of sexual size dimorphism in seabirds of the Southern Hemisphere. Oikos , 68/1: 139-145. Accessed January 24, 2008 at http://links.jstor.org/sici?sici=0030-1299%28199310%2968%3A1%3C139%3APOSSDI%3E2.0.CO%3B2-N .

Freedman, B. 2003. Figatebirds. Pp. 197-198 in Grizmek's Animal Life Encyclopedia , Vol. Vol 8, Birds 1, Second Edition. Farmington Hills, MI: Gale.

Harrison, P. 1983. Seabirds; An Identification Guide . Boston: Houghton Mifflin.

2001. Christmas Island Frigatebird; Fregata andrewsi. Pp. 104-110 in Threatened Birds of Asia: The Birdlife International Red Data Book . Cambridge, U.K.: Birdlife International. Accessed March 09, 2008 at birdbase.hokkaido-ies.go.jp/rdb/rdb_en/fregandr.pdf .

Department of the Environment and Heritage. National Recovery Plan for the Cristmas Island Figatebird; Fregata andrewsi. ISBN: 0 642 5508 5. Canberra, AU: Commonwealth of Australia. 2004.

Department of the Environment and Heritage. The Action Plan for Austrlian Birds 2000. ISBN: 0 642 54683 5. Canberra, AU: Environment Australia. 2000. Accessed March 09, 2008 at http://www.environment.gov.au/biodiversity/threatened/publications/action/birds2000/pubs/ci-frigatebird.pdf .