Taxonomy and Systematics
The cormorant family Phalacrocoracidae has traditionally been included – like all other birds with fully webbed toes – in the Pelecaniformes. But the namesake pelicans (Pelecanidae) are actually closer relatives of storks (Ciconiidae) than of cormorants. Hence, it has been proposed to separate the Phalacrocoracidae and relatives as order Phalacrocoraciformes.
This species is here placed in the catch-all genus Phalacrocorax. Modern authors generally are reserved about uniting all cormorants in one "wastebin genus", but no general revision has been published that has any phylogenetic merit. Though it was proposed to place the Pelagic Cormorant in Stictocarbo for example, this is quite certainly wrong, as the present species is by no means closely related to the Spotted Shag (P. punctatus), the type species of Stictocarbo. Similarly, Leucocarbo would refer to the group around the Imperial Shag (P. atriceps) complex, which occurs on the opposite end of the Earth from P. pelagicus. The supposed "cliff shag" subfamily Leucocarboninae is entirely paraphyletic cannot be accepted as originally circumscribed. If subfamilies are to be accepted in the Phalacrocoracidae, the Pelagic Shag and its relatives would go in the Phalacrocoracinae like most Northern Hemisphere cormorants and shags, while Leucocarboninae would include mainly Southern Hemisphere taxa.
In fact, the correct genus name for the Pelagic Cormorant, if Phalacrocorax is to be split up, would be Compsohalieus. This name would apply to the group around its type species (Brandt's Cormorant, P. penicillatus). This is a North Pacific clade, which apart from Brandt's and the Pelagic Cormorant also includes the Red-faced Cormorant (P. urile) and probably also the extinct Spectacled Cormorant (P. perspicillatus). They all have black feet, and in breeding plumage grow white filoplumes on the head and/or neck, and usually also two head-crests and white thigh patches like the present species does. They also share the back-thrown head during the "yawning" and the rapid wing-flutter in courtship display. Among the Compsohalieus group, the Red-faced Cormorant is the sister species of P. pelagicus. Apart from loking almost alike, these two species also "yawn" many times in a row instead of giving the display just once, twist their bodies before taking flight during courtship, and the male and female post-landing calls are identical. The point-and-gargle response to threats is also an apomorphy of these two species.
Its traditional scientific name is the literal Latinized Ancient Greek equivalent of the common name: Phalacrocorax is an ancient term for cormorants; literally, it means "bald raven", from falakrós (φᾶλακρός, "bald") + kórax (κόραξ, "raven"). pelagicus is – like the English loanword "pelagic" – derived from pelágios (πελᾶγιος, "of the open seas"). Compsohalieus, meanwhile, means "sleek fisher"; it derives from kompsós (κομψός, "elegant" or "sleek") + (h)alieus (ἇλιεύς, "fisherman").
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