The family Fregatidae includes a single genus (Fegata), and five species. These five species can be found along the tropical and subtropical coasts worldwide. Though in actuality only three of the five species are actually worldwide in distribution (the magnificent, great, and lesser friagtebirds). The other two are endangered and found on a single island (for each): the Christmas Island frigatebird, and the Ascension Island frigatebird.

The most distinguishing feature of this family are the red gular (throat) pouches that the male will inflate during the breeding season to attract a mate.

While they are ‘sea’ birds–their feathers are actually not ‘water-proof’ like other birds, so they feed by skimming the surface of the water for fish, squid, jellyfish, and plankton. They’re also known to steal food from other seabirds (a habit known as kleptoparastic feeding), in addition to occasionally stealing eggs and young of other sea birds.

While there are two that are listed as endangered (mainly due to predation and limited breeding areas), the other three species are also at ‘risk’ due to over-fishing by humans, parasites, and other concerns related to living near and on the oceans.

Reference: https://en.wikipedia.org/wiki/frigatebird