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How are pelicans classified differently in some modern bird taxonomies?

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Three eastern white pelicans with black-tipped wings take off from a muddy shoreline, wings outstretched, with blurred green vegetation in the background. — Pelecaniform European white pelicans (*Pelecanus onocrotalus*) in flight.

While traditional taxonomy groups pelicans with cormorants, anhingas, frigate birds, and gannets and boobies within the order Pelecaniformes, modern genetic analysis has led to significant revisions.12

In many contemporary classifications, the aforementioned seabirds are moved to a separate order called Suliformes. Under this revised taxonomy, the order Pelecaniformes is redefined to include pelicans alongside:12

Herons and egrets (family Ardeidae)
Ibises and spoonbills (family Threskiornithidae)
The hammerhead (Scopus umbretta)
The shoebill (Balaeniceps rex)12

Additionally, some taxonomies place tropic birds into their own distinct order, Phaethontiformes, as they differ significantly from other members of the traditional group. These shifts reflect ongoing debates among ornithologists regarding whether the original order represented a natural evolutionary unit or if shared traits, such as webbed feet, resulted from convergent evolution.13