FRIGATEBIRDS: Fregatidae

PHYSICAL CHARACTERISTICS

Frigatebirds (FRIGG-it-birdz) are unusual seabirds. Their feathers are not waterproof, so they try to avoid getting them wet. They have mostly dark feathers, although many frigatebirds, especially the females and young ones, have white feathers on their breasts, and some young birds have white heads. The birds also have short legs, webbed feet, forked tails, and the males have an inflatable pouch on their throats.

Frigatebirds have extremely long, pointed wings. In fact, they have the largest wings in proportion to their weight of any other bird. They also have exceptionally strong breast muscles that work together with their wings to make them powerful, acrobatic fliers.

Female frigatebirds are somewhat larger than the males. The birds are between 30 and 44 inches (75 and 112 centimeters) long from their bills to the end of their tails, and their wingspan is between 69 and 91 inches (176 and 230 centimeters). They weigh up to 3.3 pounds (1.5 kilograms), and almost half of their body weight consists of breast muscles and feathers.

GEOGRAPHIC RANGE

Magnificent frigatebirds fly above the warm ocean water and breed on tropical and subtropical islands all around the world. The other four species of frigatebirds are more rare, and each species breeds on only a few remote islands.

HABITAT

Frigatebirds breed in colonies with other frigatebird on tropical islands. The warm water near their islands is about 77°F (25°C). They choose islands that are near water with plenty of flying fish, fish that jump and glide in the air before falling back into the water.

DIET

Flying fish are the main diet of frigatebirds. They also snatch fish and other animals at the sea's surface. They attack other seabirds in the air and steal their prey. Frigatebirds sometimes eat the eggs and young of other seabirds, as well as fish scraps thrown overboard by fishing boats.

BEHAVIOR AND REPRODUCTION

During the day, frigatebirds spend moat of their time in the air. They usually search for food around their home islands, but they sometimes fly far out over the ocean when they are not breeding. They may breed at any time of year. Male birds sit at a nest site and blow up their throat pouches to attract females. They prefer to build their nests in low shrubs or trees, but sometimes they put them on the bare ground. They lay just one egg, and the young bird learns to fly between the age of five and seven months. After that, it is still dependent on its parents for food for another two to six months.

FRIGATEBIRDS AND PEOPLE

People have used to use frigatebirds to carry messages between islands in the South Pacific. Now the birds are mainly a tourist attraction.

SKY PIRATES

Frigatebirds usually catch their own meals, but they are famous for the way they steal food from other birds. In fact, they were named after the fast frigate ships used by pirates who robbed other ships at sea. When a frigatebird notices that another seabird has caught a fish, it often dives at the seabird like a fighter jet and jabs it until it drops the fish. If the seabird has already swallowed its meal, the frigatebird may grab it by the neck, tail, or wing and dangle it until it coughs up its load. Instantly, the frigatebird swoops down and snatches its free lunch.

CONSERVATION STATUS

The Ascension frigatebird is listed as Critically Endangered, facing an extremely high risk of extinction, and the Christmas frigatebird is considered Vulnerable, facing a high risk of extinction. Both lost much of their habitat when people developed the islands where they breed, and they do not like to be disturbed by people who come to watch and photograph them close-up. But their biggest trouble is the variety of mammals brought to the islands by people. Rats, pigs, goats, and pet cats eat the frigatebirds' eggs and chicks, and they destroy the plants the birds need in breeding areas.

MAGNIFICENT FRIGATEBIRD (Fregata magnificens): SPECIES ACCOUNT

Physical characteristics: Magnificent frigatebirds are the largest of the frigatebirds, with a length of 41 to 44 inches (104 to 112 centimeters) from bill to tail, and they weigh between 3.1 and 3.3 pounds (1.4 and 1.5 kilograms). Their straight gray bills are hooked at the end. They have such short legs that they cannot walk on land or swim on the water, but their strong claws help them cling to the branches where they roost and build their nests. The adult female has a white breast and some brown feathers on the top of her wings. The adult male has a mostly black body with a red throat sac.

No other birds in the world have wings as large in proportion to their weight as magnificent frigatebirds. Their wingspan is 85 to 91 inches (216 to 231 centimeters). The birds' strong breast muscles work together with their wings, making them able to fly fast and soar high, and their forked tails help them steer.

Geographic range: Magnificent frigatebirds breed on tropical and subtropical islands in the Atlantic and Pacific Oceans near North andSouth America. Some also breed in mangrove trees along the coasts. Colonies of the birds are also found off the western coast of Africa. They usually roam the waters near their home islands, but they sometimes fly far out over the ocean.

Habitat: The ideal habitat for a colony of magnificent frigatebirds is a tropical island with mangroves or other trees and bushes for nesting surrounded by an ocean full of flying fish.

Diet: Magnificent frigatebirds feed on flying fish that they catch in the air up to 6 or more feet (1.8 or more meters) above the surface of the ocean. They also eat other small fish, as well as squid, young turtles, crabs, and jellyfish. Frigatebirds snatch this prey from the surface of the water. They like the eggs and chicks of other seabirds when they can get them, and they eat the fish parts discarded by fishing boats. Sometimes they steal the prey of other seabirds in midair.

Behavior and reproduction: Magnificent frigatebirds never land on water, except accidentally. Their feathers are not waterproof and quickly become wet and heavy in the water, making it difficult for them to take off. Instead, they spend their daytime hours in the air, and they perch in bushes or on tree braches when they roost each night. They are exceptionally skillful at catching fish and other sea animals while flying right above the surface of the water. Strong winds do not bother them—they can even ride out a hurricane in flight.

At breeding time, the males gather in trees or bushes about pecking distance from each other. It takes the males about twenty-five minutes to blow up their red "balloons." They do it by sucking air into the wrinkled red pouches on their throats. Then they shake their wings and rattle their bills. The females fly overhead and check them out. Then, each one chooses a male as her mate. The pairs build their flat nests of twigs, sticks, and grasses right on the spots where the males were showing off. The males often steal nest material from each other or from other seabirds nesting nearby. The birds are noisy at the nest site, although they are quiet at sea.

Each female lays just one egg, and she will take care of this young bird for more than a year. For about two months, the parents take turns sitting on the egg. The young bird is naked and helpless when it hatches. But soon the chick starts begging loudly to be fed, and it eats food that the parents regurgitate (re-GER-jih-tate; spit up). Before the chick is three months old, its father leaves. After that, the female continues to feed the young bird long after it learns to fly. Young frigatebirds practice catching food on the wing by dropping feathers and seaweed. It takes them a long time to learn how to feed themselves. Females breed every other year, and young birds are ready to breed by the age of seven.

Magnificent frigatebirds and people: These birds have become a favorite of bird-watching tourists, and the money the tourists spend on boat tours, hotels, and food helps the local people who live near the birds.

Conservation status: Magnificent frigatebirds have suffered from loss of habitat at many of their breeding places. Fishing boats have over-fished some of the ocean areas where the birds used to find their food. However, the birds are not in danger of extinction (dying out). ∎

FOR MORE INFORMATION

Books:

Alsop, Fred J. III. Smithsonian Birds of North America. London and New York: D.K. Publishing, 2001.

del Hoyo, Josep, A. Elliott, and J. Sargatal, eds. Handbook of the Birds of the World. Vol. 1, Ostrich to Ducks. Barcelona: Lynx Edicions, 1992.

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

Kaufman, Kenn. Lives of North American Birds. New York: Houghton Mifflin, 1996.

Soper, Tony. Oceans of Seabirds. London: David and Charles Publishers, 1989.

Periodicals:

Diamond, Antony W., and Elizabeth A. Schreiber. "The Birds of North America, Magnificent Frigatebird, No. 601." Cornell Laboratory of Ornithology and The Academy of Natural Sciences (2002): 1–24.

Fountain, Henry. "Tracking High Fliers." The New York Times (January 28, 2003): D3.

Pitz, Mary Elisabeth. "Pirates in Paradise." Birder's World (April 2001): 56.

Weimerkirch, Henri, Olivier Chastel, Christophe Barbraud, and Olivier Tostain. "Frigatebirds Ride High on Thermals." Nature (January 23, 2003): 333–334.

Web sites:

"Frigatebirds." Rochester Institute of Technology, Galápagos Pages. http://www.rit.edu/rhrsbi/GalapagosPages/Frigatebirds.html (accessed on April 8, 2004).

"Magnificent Frigatebird, Fregata magnificens." eNature.com. http://www.enature.org/main/home.asp (accessed on April 9, 2004).

"Frigatebirds (Man-of-War)." GBR Explorer, Great Barrier Reef Marine Park Authority. http://www.reefed.edu.au/explorer/animals/marine_vertebrates/seabirds/frigatebirds.html (accessed on April 9, 2004).