generally long-lived birds, with several species known to live in excess of 30 years. Skimmers are a small family of tropical tern-like birds. They have an elongated lower mandible which they use to feed by flying low over the water surface and skimming the water for small fish. Tropicbirds Order: PhaethontiformesFamily: Phaethontidae Tropicbirds are slender white birds of tropical oceans, with exceptionally long central tail feathers. Their heads and long wings have black markings. Penguins Order: SphenisciformesFamily: Spheniscidae The penguins are a group of flightless aquatic birds living almost exclusively in the Southern Hemisphere. Most penguins feed on krill, fish, squid, and other forms of marine life caught while swimming underwater. Albatrosses Order: ProcellariiformesFamily: Diomedeidae The albatrosses are among the largest of flying birds, with those of the genus Diomedea having the largest wingspan of any extant bird. Southern storm-petrels Order: ProcellariiformesFamily: Oceanitidae The storm-petrels are the smallest seabirds, relatives of the petrels, feeding on planktonic crustaceans and small fish picked from the surface, typically while hovering. The flight is fluttering and sometimes bat-like. Until 2018, this family's species were included with the other storm-petrels in family Hydrobatidae. Northern storm-petrels Order: ProcellariiformesFamily: Hydrobatidae Though the members of this family are similar in many respects to the southern storm-petrels, including their general appearance and habits, there are enough genetic differences to warrant their placement in a separate family. Shearwaters and petrels Order: ProcellariiformesFamily: Procellariidae The procellariids are the main group of medium-sized "true petrels", characterised by united nostrils with medium septum and a long outer functional primary. Storks Order: CiconiiformesFamily: Ciconiidae Storks are large, long-legged, long-necked wading birds with long stout bills. Storks are mute, but bill-clattering is an important mode of communication at the nest. Their nests can be large and may be reused for many years. Many species are migratory. Frigatebirds Order: SuliformesFamily: Fregatidae Frigatebirds are large seabirds usually found over tropical oceans. They are large, black, or black-and-white, with long wings and deeply forked tails. The males have coloured inflatable throat pouches. They do not swim or walk and cannot take off from a flat surface. Having the largest wingspan-to-body-weight ratio of any bird, they are essentially aerial, able to stay aloft for more than a week. Boobies and gannets Order: SuliformesFamily: Sulidae The sulids comprise the gannets and boobies. Both groups are medium to large coastal seabirds that plunge-dive for fish. Anhingas Order: SuliformesFamily: Anhingidae Anhingas or