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To the Beauty of Birds

The Great Frigatebird, Fregata minor, is a large seabird in the frigatebird family Fregatidae which has only a single genus Fregata. Major nesting populations are found in the Pacific (including the Galapagos Islands) and Indian Oceans as well as the South Atlantic. The Great Frigatebird measures 33 to 41 inches in length with long pointed wings of 80.5–90.5 in and long forked tails. It weighs from 1.4–3.4 lb.
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.

The Lesser Frigatebird, Fregata ariel, is also a species of frigatebird.
The members of the genus Fregata are:

Magnificent Frigatebird or Man of War, Fregata magnificens
Ascension Frigatebird, Fregata aquila
Christmas Frigatebird, Fregata andrewsi
Great Frigatebird, Fregata minor
Lesser Frigatebird, Fregata ariel

The Lesser Frigatebird or Least Frigatebird is said to be the most common and widespread frigatebird in Australian seas. It is common in tropical seas breeding on remote islands, including Christmas Island in the Indian Ocean in recent years.
It is the smallest of the three frigatebirds found measuring about 30 inches in length versus 33+ inches for the Great Frigatebird and 39 inches for the Magnificant Frigatebird. Like all frigatebirds the male has a large red sac on the front of the throat which is inflated during courtship.

It can be seen that differentiating between the three major frigate birds is not easy. Size differences are difficult to judge at a distance. The major difference is that the Lesser Frigatebird has white at the junction of the wings with the body and a black head (top and bottom) while the great frigatebird does not have this white under the wings and the bottom part of the head is white (see figure).

The male is mostly all black save for a white patch on the flank which extends on to the underwing as a spur. Males also have a pale bar on the upper wing.
Females have a black head and neck with a white collar and breast as well as a spur extending on to the underwing. The female also has a narrow red ring around the eye.
Juveniles and immature birds are more difficult to differentiate but the presence of the spurs of white in the armpits is a helpful distinguishing sign.

Great and Lesser Frigatebird

Great Frigatebird 2192

Great Frigatebird 2193

Great Frigatebird 2497

Great Frigatebird 2191

Lesser Frigatebird 3148

Lesser Frigratebird 2274

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lesser