Great Frigatebird

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Hawaiian Name: iwa
Common Name: Great Frigatebird
Scientific Name: Fregata minor

Size: 33-41 inches (85-105 cm); 205–230 cm Wingspan

Habitat: Tropical Oceans; Hawaii is the northernmost extent of their range in the Pacific Ocean, with around 10,000 pairs nesting mostly in the Northwestern Hawaiian Islands. In the Central and South Pacific, colonies are found on most islands Groups from Wake Island to the Galapagos Islands to New Caledonia with a few pairs nesting on Australian possessions in the Coral Sea. Colonies are also found on numerous Indian Ocean islands including Aldabra, Christmas Island, Maldives and Mauritius. The small populations in the Western Atlantic Ocean may still persist but are very small if they do. Great Frigatebirds undertake regular migrations across their range, both regular trips and more infrequent widespread dispersals. Birds marked with wing tags on Tern Island in French Frigate Shoals were found to regularly travel to Johnston Atoll (873 km), one was reported in Quezon City in the Philippines. Despite their far ranging birds also exhibit philopatry, breeding in their natal colony even if they travel to other colonies.

The Great Frigatebird forages in pelagic waters within 80 km (50 mi) of the breeding colony or roosting areas.

Status: Least Concern. Global Population: 340,000 - 1,000,000 mature individuals. The population is suspected to be in decline owing to ongoing habitat destruction and unsustainable levels of exploitation.

Diet: Flying fish, other fish species and squid. Prey is snatched while in flight, either from just below the surface or from the air in the case of flying fish flushed from the water.

Nesting: Male Great Frigatebirds are smaller than females, but the extent of the variation varies geographically. The plumage of males is black with scapular feathers that have a purple-green iridescence when they refract sunlight. Females are black with a white throat and breast and have a red eye ring. Juveniles are black with a rust-tinged white face, head and throat.

Great Frigatebirds are seasonally monogamous, with a breeding season that can take two years from mating to the end of parental care. The species is colonial, nesting in bushes and trees (and on the ground in the absence of vegetation) in colonies of up to several thousand pairs. Nesting bushes are often shared with other species, especially Red-footed Boobies and other species of frigatebirds.

Both sexes have a patch of red skin at the throat that is the gular sac; in male Great Frigatebirds this is inflated in order to attract a mate. Groups of males sit in bushes and trees and force air into their sac, causing it to inflate over a period of 20 minutes into a startling red balloon. As females fly overhead the males waggle their heads from side to side, shake their wings and call. Females will observe many groups of males before forming a pair bond. After forming a bond the pair will choose a nesting site, which may be at the display site or another location; once a nesting site has been established both sexes will defend their territory (the area surrounding the nest that they are able to reach) from other frigatebirds.

Pair bond formation and nest-building can be completed in a couple of days by some pairs and can take a couple of weeks (up to four) for other pairs. Males collect loose nesting material (twigs, vines, flotsam) from around the colony and off the ocean surface and return to the nesting site where the female builds the nest. Nesting material may be stolen from other seabird species (in the case of Black Noddies the entire nest may be stolen) either snatched off the nesting site or stolen from other birds themselves foraging for nesting material. Great Frigatebird nests are large platforms of loosely woven twigs that quickly become encrusted with guano. There is little attempt to maintain the nests during the breeding season and nests may disintegrate before the end of the season.

A single dull chalky-white egg measuring 68 x 48 mm is laid during each breeding season. If the egg is lost the pair bond breaks; females may acquire a new mate and lay again in that year. Both parents incubate the egg in shifts that last between 3–6 days; the length of shift varies by location, although female shifts are longer than those of males. Incubation can be energetically demanding, birds have been recorded losing between 20–33% of their body mass during a shift.

Incubation lasts for around 55 days. Great Frigatebird chicks begin calling a few days before hatching and rub their egg tooth against the shell. The altricial chicks are naked and helpless, and lie prone for several days after hatching. Chicks are brooded for two weeks after hatching, during this time they become covered in white down. Then they are guarded by a parent for another fortnight. Chicks are given numerous meals a day after hatching, once older they are fed every one to two days. Feeding is by regurgitation, the chick sticks its head inside the adult’s mouth.

Fledging occurs after 4–6 months, the timing dependent on oceanic conditions and food availability. In bad years (particularly El Niño years) the period of care is longer. After fledging chicks continue to receive parental care for between 150–428 days; frigatebirds have the longest period of post-fledging parental care of any bird. The diet of these juvenile birds is provided in part by food they obtained for themselves and in part from their parents. Young fledglings will also engage in play; with one bird picking up a stick and being chased by one or more other fledglings. After the chick drops the stick the chaser attempts to catch the stick before it hits the water, after which the game starts again. This play is thought to be important in developing the aerial skills needed to fish.

Cool Facts: The Great Frigatebird is a large seabird and, despite its name, it is the second largest frigatebird, after the Magnificent Frigatebird. The frigatebirds have the highest ratio of wing area to body mass, and the lowest wing loading of any bird. It has been hypothesized that this enables the birds to utilize marine thermals created by small differences between tropical air and water temperatures.

The Hawaiian name, iwa, means “thief”.

Found in Songbird ReMix Hawai'i

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