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The 'Pelecaniformes' are an order of medium-sized and large waterbirds found worldwide. They are distinguished from other birds by the possession of feet with all four toes webbed (totipalmate). Most have a bare throat patch (gular patch). There are some 50-60 living species, depending on which families are placed in this group.
They feed on fish, squid or similar marine life. Nesting is colonial, although birds are monogamous, and the young are born helpless — in contrast, for example, to many waders.

Contents

Systematics and evolution

List of Pelecaniformes families

References

Systematics and evolution

Sibley and Ahlquist's landmark DNA-DNA hybridisation studies (See: Sibley-Ahlquist taxonomy) led to them placing the families traditionally contained within the Pelecaniformes together with the grebes, cormorants, ibises and spoonbills, New World vultures, storks, penguins, albatrosses, petrels, and loons together as a sub-group within a greatly expanded order Ciconiiformes, a radical move which by now has been all but rejected: their "Ciconiiformes" merely assembled all early advanced land- and seabirds for which their research technique delivered insufficient phylogenetic resolution.
Recent research strongly suggests that the similarities between the Pelecaniformes as traditionally defined are the result of convergent evolution rather than common descent, and that the group is paraphyletic (Mayr, 2003). All families in the traditional or revised Pelecaniformes except the Phalacrocoracidae have only a few handfuls of species at most, but many were more numerous in the early Neogene. Fossil genera and species are discussed in the respective family or genus accounts; two little-known prehistoric pelecaniforms, however, cannot be classified accurately enough to assign them to a family. They are ''"Sula" ronzoni'' from Early Oligocene rocks at Ronzon (France), which was initially believed to be a sea-duck and possibly is an ancestral pelecaniform, and a Pleistocene fossil from Australia apparently related to darters and described as ''?Anhinga laticeps''.
The "pelecaniform" lineages appear to have originated around the end of the Cretaceous. Monophyletic or not, they appear to belong to a close-knit group of "higher waterbirds" which also includes groups such as penguins and Procellariiformes. It is interesting to note that there are quite a lot of fossil bones from around the Cretaceous-Paleocene boundary which cannot be firmly placed with any of these orders and rather combine traits of several of them. This is of course only to be expected, if the theory that most if not all of these "higher waterbird" lineages originated around that time is correct. Of those apparently basal taxa, the following show some similarities to the traditional Pelecaniformes:

★ ''Lonchodytes'' (Lance Creek Late Cretaceous of Wyoming, USA)

★ ''Torotix'' (Late Cretaceous)

★ ''Tytthostonyx'' (Late Cretaceous/Early Palaeocene)

★ ''Cladornis'' (Deseado Early Oligocene of Patagonia, Argentina)

★ ''Liptornis'' - a ''nomen dubium''

List of Pelecaniformes families

★ 'Fregatidae': frigatebirds. A group of five closely related large birds with black and white plumage, very long wings, and parasitical hunting habits. Red throat patches are inflated in display.

★ 'Pelecanidae': pelicans. Very large birds with throat pouches in which they catch and store fish while hunting.

★ 'Pelagornithidae': pseudotooth birds. A family of gigantic seabirds that looked similar to albatrosses, but had a large bill with tooth-like projections that enabled them to pick up slippery prey like fish or squids more easily.

★ 'Sulidae': gannets and boobies. Medium to large species which hunt by diving from the air into the sea (plunge diving). Long wings and bills, often coloured feet.

★ 'Phalacrocoracidae': cormorants and shags. Medium to large with hooked bills and usually black or similar dark plumage. Plumage is not fully waterproof.

★ 'Anhingidae': darters. Another small closely related group of four species, with long bills, snake-like necks and the ability to swim with their body submerged. Plumage is not fully waterproof.

★ 'Protoplotidae': an extinct family which apparently is derived from the same ancestor as the anhingas, but is very badly known.
The following families are traditionally placed into the Pelecaniformes, but probably do not belong there:

★ 'Plotopteridae': plotopterids or diving-"boobies". An extinct group of penguin-like seabirds. Possibly link penguins and pelecaniforms, in which case they would possibly have to be placed in a distinct order.

★ 'Phaethontidae': tropicbirds. Medium-sized birds, adapted to a matrine lifestyle similar to frigatebirds. Adults have long central tail feathers and no gular patch. Apparently closer to Procellariiformes (Mayr, 2003; Bourdon ''et al.'', 2005) and might form a separate order, together with the

★ 'Prophaethontidae': a little-known prehistoric family closely allied to the tropicbirds.
The shoebill and the hammerkop, which make up the monotypic families (Balaenicipitidae and Scopidae, respectively) usually placed with the traditional Ciconiiformes, may be very distinct pelecaniform lineages instead.

References

★ 'Bourdon', Estelle; Bouya, Baâdi & Iarochene, Mohamed (2005): Earliest African neornithine bird: A new species of Prophaethontidae (Aves) from the Paleocene of Morocco. ''J. Vertebr. Paleontol.'' '25'(1): 157-170. DOI: 10.1671/0272-4634(2005)025[0157:EANBAN]2.0.CO;2 HTML abstract

★ 'Mayr', Gerald (2003): The phylogenetic affinities of the Shoebill (''Balaeniceps rex''). ''Journal für Ornithologie'' '144'(2): 157-175. [English with German abstract] HTML abstract