Lesser Frigatebird

The Lesser Frigatebird is the smallest of the five frigatebird species, sharing the family's long, angular wings and deeply forked tail but with a noticeably lighter, more buoyant flight due to its reduced size. Adult males are glossy black with a green sheen and the typical inflatable red throat pouch, distinguished from other frigatebirds by white patches on the sides of the breast that extend as a spur onto the underwing. Females have a black head, white breast extending further onto the flanks, and a dark throat, differing from the pale throat of female Great Frigatebirds.

Highly aerial and pelagic, Lesser Frigatebirds range widely over tropical seas of the Indian and Pacific Oceans, nesting in scattered colonies on remote islands.

Key field marks

• Smallest frigatebird, with slimmer, lighter build
• White axillary "spur" patches on the flanks/underwing sides, present in both sexes
• Males otherwise all black with green gloss and red throat pouch
• Females show a black throat and head contrasting with white breast

Similar species

• Great Frigatebird is larger and lacks the white flank spurs; female Great Frigatebirds have a pale throat rather than the dark throat of Lesser Frigatebird females.
• Christmas Island Frigatebird and Ascension Frigatebird are rarer, geographically restricted relatives with more localized ranges.
• Juveniles have rusty or white heads, further complicating identification, and require careful attention to underwing pattern.

Lesser Frigatebirds breed on remote tropical islands across the Indian and Pacific Oceans, including sites in northern Australia, the Seychelles, and various Pacific atolls, generally favoring low vegetation for nesting on predator-free islets. They are highly pelagic outside the breeding season, ranging over vast expanses of open tropical ocean.

The species can wander considerable distances, with vagrants occasionally recorded far outside their normal range, sometimes assisted by strong tropical storm systems.

Behavior

Like other frigatebirds, Lesser Frigatebirds are aerial kleptoparasites and surface feeders, harassing other seabirds to steal food and snatching prey from the ocean surface without landing.

Voice

Males rattle their bill against the inflated pouch and give whistling calls during courtship displays at the colony; otherwise they are relatively quiet at sea.

Feeding

Small fish and squid taken at the surface make up the bulk of the diet, supplemented by food stolen from boobies, terns, and tropicbirds.

Nesting and breeding

Colonies form on low trees, shrubs, or even bare ground on predator-free islands; a single egg is laid, and chick-rearing is prolonged, with young frigatebirds remaining dependent on parents for many months after fledging.