RECENT work on tho great frigate-bird Fergata minor of the Galapagos island of Tower disclosed a unique syndrome of adaptations to a markedly erratic and non-seasonal food supply. The Fergatidae have not only evolved a strongly aerial life, becoming morphologically specialized with reduced tarsi, tiny unwebbed zygodactylous feet, vestigial uropygial gland (plumage water-proofing unnecessary) and a ratio of wing span to weight greater than in any other sea-bird (about four times as great as the comparably sized, sympatric and far-flying waved albatross (Diomedea irrorata)) but, if Fergata minor is typical, they also differ from all other members of their order Pelicaniformes in several basic reproductive mechanisms.