The Christmas frigatebird is a large lightly built seabird with brownish-black plumage, long narrow wings and a deeply forked tail.

The male has an egg shaped white patch on his belly and a striking red gular sac which he inflates to attract a mate.

[1] The Christmas frigatebird was once considered to belong to the species Fregata aquila but in 1914 the Australian ornithologist Gregory Mathews proposed that the Christmas frigatebird should be considered as a separate species with the binomial name Fregata andrewsi in honour of the English paleontogist Charles Andrews.

Other plumages resemble those of the smaller lesser frigatebird, but have whiter bellies and longer white underwing spurs.

Populations, however, continue to decline due to persecution by fishermen, loss of breeding habitat associated with phosphate mining, marine pollution and entanglement in fishing equipment.