The frigatebirds (also known as Fregatidae) are a family of seabirds. They have long wings, tails, and bills and the males have a red gular pouch that is inflated during the breeding season to attract a mate. Their plumage is predominantly black. There are five species, all in a single genus Fregata, found across all tropical and subtropical oceans. They are absent from polar regions.
Frigatebirds are pelagic piscivores that obtain most of their food on the wing. A small amount of their diet is obtained by robbing other seabirds and by snatching seabird chicks. Frigatebirds are seasonally monogamous and nest in colonies. A rough nest is constructed in low trees or on the ground on remote islands. A single egg is laid each breeding season. The duration of parental care in frigatebirds is among the longest for birds.
I also read the reason they steal food, is they don't have the oil that makes their feathers waterproof, so they do not dive as other sea birds do, the stealing food and their large ominous black bodies make them known as the Pirates of the seabird world.
The word frigatebird derives from the French mariners' name for the bird La Frégate - a frigate or fast warship. The etymology was mentioned by French naturalist Jean-Baptiste du Tertre when describing the bird in 1667. In the Caribbean frigatebirds were called Man-of-War birds by English mariners. This name was used by the English explorer William Dampierin his book An Account of a New Voyage Around the World published in 1697: