Great Frigatebird Life History

Habitat

Great Frigatebirds live on small, remote islands in the tropical and subtropical waters of the Indian and Pacific Oceans. They nest in trees or shrubs when available. During the nonbreeding season, Great Frigatebirds forage over vast areas of open ocean, feeding in highly saline waters with surface temperatures above 22°C (72°F). Although they can rest on the wing and therefore do not need to come to land to roost, they do roost on islands when they are available.

Food

Great Frigatebirds feed mainly on flying fish and squid. They spend most of their time soaring high above the ocean, and then drop down to snatch prey from just below the water surface, without landing. They often feed over schools of predatory fish that drive smaller fish to the surface. Great Frigatebirds forage alone, in pairs, or with mixed-species feeding flocks of Sooty Terns, Wedge-tailed Shearwaters, and other seabirds. Like other frigatebirds, Great Frigatebirds sometimes steal food from other seabird species (the technical term for this is "kleptoparasitism")—chasing boobies, tropicbirds, petrels, and other seabirds until they drop or regurgitate food items and then swooping down to catch the item before it hits the water. Though they're famous for their piracy, behavioral studies indicate that most frigatebirds get only about 5% of their food this way.

Nesting

Nest Placement

Typically placed on or near the tops of trees and bushes.

Nest Description

A large, loose platform made of sticks, twigs, vines and leaves. The male gathers most of the nesting material and the female constructs the nest. Individuals often take nesting material from the nests of boobies and other frigatebirds.

Nesting Facts

Behavior

Great Frigatebirds are highly specialized for flight. Their long, narrow wings and relatively light bodies allow them to soar for hours or even days with only occasional deep wingbeats. At the same time, their deeply forked tail provides great maneuverability, allowing them to chase other seabirds and harass them into dropping their food. When soaring high in the sky, frigatebirds hold their wings in a distinctive M-shaped crook and bring their forked tail together into a single long point. Frigatebirds have very small legs and feet, with reduced webbing, rendering them incapable of walking or swimming.

Great Frigatebirds are social birds, roosting communally and often soaring in loose groups. They nest in colonies that may contain several thousand pairs and often include other species, such as Lesser and Magnificent Frigatebirds and Red-footed Boobies. Male Great Frigatebirds form display groups, perching close together in a bush to advertise to females overhead. The males inflate their bright red throat pouches (gular sacs), point their bills skyward, shake their outstretched wings, and deliver a warbling vocalization. Pairs are monogamous but likely remain together for just a single breeding season. Both sexes incubate the single egg and brood and feed the chick. The nestling grows very slowly, usually remaining in the nest for 120–160 days before fledging. Frigatebirds have the longest period of postfledging parental care of any bird species, with the fledgling fed for 150–428 days after leaving the nest. Due to this protracted breeding cycle, female Great Frigatebirds (and likely males as well) can only successfully breed every two years.

Conservation

The International Union for Conservation of Nature lists Great Frigatebird's conservation status as Least Concern and estimates the global population size at 120,000 mature individuals.

Credits

BirdLife International. 2020. Fregata minor. The IUCN Red List of Threatened Species 2020: e.T22697733A163770613. https://dx.doi.org/10.2305/IUCN.UK.2020-3.RLTS.T22697733A163770613.en.

Gauger Metz, V. H. and E. A. Schreiber (2020). Great Frigatebird (Fregata minor), version 1.0. In Birds of the World (S. M. Billerman, Editor). Cornell Lab of Ornithology, Ithaca, NY, USA.

Weimerskirch, H., Borsa, P., Cruz, S., de Grissac, S., Gardes, L., Lallemand, J., Corre, M.L. and Prudor, A. (2017), Diversity of migration strategies among great frigatebirds populations. J Avian Biol, 48: 103-113. https://doi.org/10.1111/jav.01330

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