Lesser Frigatebird | Fregata ariel

Voice

At sea it is entirely silent. At the colony the male drums with his bill on the inflated red throat sac and delivers a tremulous, gurgling warble that recalls a rattle turning in the distance. Females and young give a hard, yapping croak at the nest and when quarrelling over a perch.

Identification

An all-black seabird of sixty-six to eighty-one centimetres with long, sharply angled wings and a deeply forked tail usually carried closed to a point in flight. The male is black with a brown bar across the upperwing and a white spur running from the flank into the axillaries; in display he inflates a scarlet throat sac the size of a football. The female has a black head and throat, a white breast and collar, the same white axillary spur and a narrow red eye ring. Young birds have a rusty white head and a white belly, and show the axillary spur before the rest of the plumage matures. It almost never lands on the water, its plumage not being waterproof.

Confusion species

Great Frigatebird (Fregata minor) is bulkier and heavier-billed; the male is all black without a white flank spur, and the female has a grey throat and white breast but no white axillary spur. In young birds the white armpit is the conclusive feature: in Lesser the white of the belly runs as a sharp point into the axilla, in Great it does not. Christmas Island Frigatebird (Fregata andrewsi) is very rare in this region and the male shows a white belly patch. So on every frigatebird look at the armpit first and at the rest afterwards.

Habitat

Tropical sea over reef, atoll and the shelf edge, where it fishes behind tuna schools that drive prey to the surface. It roosts and nests on low shrubs, mangrove and Pisonia trees of uninhabited islands and cays (low sand islet on a coral reef), the colonies packed close together. It seldom passes over land, except when a cyclone drives it inland.

Range and movements

Across the tropical Indian and Pacific Oceans. In Australia at least fifteen thousand pairs breed on islands off the north coast — from Ashmore Reef and the Kimberley islands to the Coral Sea cays and the Swain Reefs — with a breeding season running roughly from May to December. Outside the breeding season birds range south along both coasts, in summer as far as New South Wales and Western Australia. On Norfolk and in New Zealand it is a vagrant, and tropical cyclones carry birds far inland and to the southern coasts.

• Resident
• dark = core range, pale = thinly spread

Where and when to look

In the north, watch from a headland or a reef boat in the late afternoon, when birds hang high above the breakers using the thermals; Michaelmas Cay off Cairns and the headlands at Darwin are proven sites. After a tropical cyclone, work the stock dams and inland reservoirs: that is where exhausted frigatebirds sit on fence posts and dead trees.

Conservation

Least Concern (LC), with a world population in the hundreds of thousands and an Australian stronghold that is large and largely uninhabited. Rats and cats on breeding islands and disturbance of colonies by visitors are the local threats; at sea birds become entangled in fishing line and drifting net. In the longer term the decline of large tuna counts, because without their hunting its food does not come to the surface.

Scientific name

Fregata ariel | (Gray, 1845)

George Robert Gray described the bird in 1845 as Atagen ariel; because it was later placed in another genus, author and year stand in parentheses. The genus Fregata was introduced by Lacépède in 1799, after French frégate, the fast sailing ship to which sailors likened the bird. ariel refers to Ariel, the spirit of the air in Shakespeare's Tempest. Gray gave no type locality; Mathews designated Raine Island, Queensland, in 1914.