Pelecaniformes

The Pelecaniformes is a (possibly invalid) order of medium-sized and large waterbirds found worldwide. As traditionally—but erroneously—defined, they encompass all birds that have feet with all four toes webbed. Hence, they were formerly also known by such names as totipalmates or steganopodes. Most have a bare throat patch (gular patch), and the nostrils have evolved into dysfunctional slits, forcing them to breathe through their mouths. They feed on fish, squid or similar marine life. Nesting is colonial, but individual birds are monogamous. The young are altricial, hatching from the egg helpless and naked in most. They lack a brood patch.

In the all-encompassing "steganopode" circumscription, the Pelecaniformes had some 50–60 living species. However, modern opinion considers the apparent similarities the result of convergent evolution, and based on a wealth of evidence splits the classically defined "Pelecaniformes" into several groups. Most lineages—frigatebirds, gannets, cormorants and anhingas—constitute indeed a natural group, for which the names Suliformes or Phalacrocoraciformes have been proposed. Tropicbirds are of unclear relationships, but appear to be a quite distinct lineage; they are typically placed in their own order, the Phaethontiformes. The pelicans (Pelecanidae), meanwhile, are linked to the storks (Ciconiidae) by two bizarre monotypic families, the Hamerkop (Scopidae) and the Shoebill (Balaenicipitidae). Indeed, they may be more closely related to storks than these are to herons. To overcome this confusion, it has been proposed to merge the "core" Pelecaniformes into the Ciconiiformes.