The pelagic cormorant (Urile pelagicus), also known as Baird's cormorant or violet-green cormorant, is a small member of the cormorant family Phalacrocoracidae. Analogous to other smallish cormorants, it is also called the pelagic shag occasionally. This seabird lives along the coasts of the northern Pacific; during winter it can also be found in the open ocean. Pelagic cormorants have relatively short wings due to their need for economical movement underwater, and consequently have the highest flight costs of any bird.

It was formerly classified in the genus Phalacrocorax, but a 2014 study supported reclassifying it and several other Pacific cormorant species into the genus Urile. The IOC followed this classification in 2021.

Description

thumb|left|Nonbreeding adult U. p. resplendens on [[Morro Rock (California, United States)]]

This is a smallish cormorant which measures in length, with a wingspan of about and a weight of when fully grown. Adults in nonbreeding plumage are all-black with a metallic iridescence. In breeding plumage they grow two short crests (one on top of the head and one at the nape), white thighs, and scattered white filoplumes on the head and neck. The long thin bill and the large feet with all-webbed toes are black throughout the year, while the patch of dark naked skin below the eye turns a vivid magenta in the breeding season.

Range

The pelagic cormorant inhabits the shores and the neritic zone of the North Pacific. Its North American range extends from Alaska to the Baja California Peninsula in Mexico. It furthermore is found on the Aleutian and other Bering Strait islands, and from the Russian Far East Chukchi Peninsula via Sakhalin south to Kamchatka, and ultimately Kyūshū (though not the rest of Japan). The subarctic populations are migratory, while the birds from temperate and subtropical regions only disperse locally after breeding, but even so Asian birds may reach China or Korea. Vagrants have been recorded in the Hawaiian Islands.

Breeding

right|thumb|Adult on a nest in [[San Luis Obispo, California, United States]]

right|thumb|A parent with approximately one-month-old chicks on a nest

The pelagic cormorant breeds on rocky shores and islands. They do not form large colonies, but smaller groups may nest together. In some cases these birds alternate between two or three nesting sites in a region from one year to another. The nest is built at the cliff face, usually on ledges, less often in crevices or caves. The nest is built from stringy plants, such as grasses or seaweed, and held together by the birds' own guano. Once the birds have found a nest site they like, they tend to remain faithful to it for the rest of their lives. The nest is repaired and improved in each season if need be; it can thus grow up to deep.

The clutch is generally between two and five eggs, most often three or four, but clutches of up to seven eggs have been recorded. Incubation lasts for 3 weeks<!-- from AnAge; check --> to one month<!-- from HBW -->. At hatching, the young weigh somewhat more than an ounce (35&nbsp;g) and are naked, but they soon grow sooty-gray down feathers. In normal years, all young of a typical clutch may be raised successfully, but less than four rarely fledge. On the other hand, during unfavorable phases of the Pacific decadal oscillation, most pairs manage to raise only two young at most. They reach sexual maturity at two years of age, and a maximum age of almost eighteen years has been recorded in the wild.

Status

This numerous and widespread species is not considered threatened by the IUCN. The bulk of its population is found in the relatively inaccessible waters of the Bering Sea region; about 50,000 each breed in the Kuril Islands, the Bering Sea islands, and the U.S. state of Alaska and its offshore islands (including the Aleuts). About 25,000 breed down the Pacific coast of North America, some 60% of which are found in California. Local populations may be all but wiped out temporarily by oil spills, and on a larger scale competition with gillnet fisheries and drowning in such nets is putting a limit to its stocks.

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. More recent evidence indicates that they and the darters actually belong in the order Suliformes, alongside the boobies and gannets.

thumb|right|The largely [[sympatric red-faced cormorant (U. urile, shown here in breeding plumage) is the pelagic cormorant's sister species]]

This species was formerly placed in the catch-all genus Phalacrocorax. Modern authors were previously reserved about uniting all cormorants in one "wastebin genus", but most revisions published had on 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.

Another theory held that the genus name for the pelagic cormorant, if Phalacrocorax was 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 looking 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. In 2014, a study was published supporting this treatment, albeit classifying the species in the genus Urile rather than Compsohalieus. The IUCN, BirdLife International, and the IOC have since followed this classification, legitimizing it. (κόραξ, "raven"). Pelagicus is – like the English loanword "pelagic" – derived from (πελᾶγιος, "of the open seas"). Compsohalieus, meanwhile, means "sleek fisher"; it derives from (κομψός, "elegant" or "sleek") + ' (ἇλιεύς, "fisherman"). Urile is a term coined by Bonaparte in 1855 as the species name for the red-faced cormorant.

However, a subsequent analysis of a larger number of comparison specimens of the pelagic cormorant – mainly from birds that fell victim to the Exxon Valdez oil spill – determined that the bones were attributable to small females of the latter species, and that their apparent distinctness was due to the original canonical analysis being distorted by insufficient specimens. The researchers also found that contrary to what was generally assumed, pelagic cormorants from the Aleutians were generally small birds – as opposed to western Alaskan individuals, which are usually very large. If the Aleutian population were to be considered a distinct subspecies, the name kenyoni would apply. Verification of subspecies status would require DNA sequence analyses however, since the differences in morphology are not large and there is much variation between individuals.

In 2003, during an USFWS survey three small pelagic cormorants whose bills appeared to be red were noted at Karab Cove on Agattu Island. It may be that these were kenyoni, but whether the bill color distinguishes the presumed subspecies or whether it is due to a simple mutation has not been determined. The large birds from the Prince William Sound region were formerly called U. p. robustus, but are not considered distinct today. Since there appear to be at least two recognizable and allopatric size groups in the northern subspecies alone, more research is clearly necessary.

Footnotes

References

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  • AnAge [2009]: Phalacrocorax pelagicus life history data. Retrieved 2009-SEP-12.
  • Byrd, G.V. & Williams, J.C. (2004): Cormorant surveys in the Near Island Group, Aleutian Islands, Alaska in July 2003 with notes on other species. U.S. Fish and Wildlife Service Reports ANMWR 03/13.
  • Christidis, Les & Boles, Walter E. (2008<!-- "2007" -->): Systematics and Taxonomy of Australian Birds. CSIRO Publishing, Collingwood, Victoria, Australia.
  • Fuller, Errol (2000): Extinct Birds (2nd ed.). Oxford University Press, Oxford, New York.
  • Hobson, K.A. (1997): Pelagic Cormorant (Phalacrocorax pelagicus). In: Poole, A. & Gill, F. (eds.): The Birds of North America 282. The Academy of Natural Sciences, Philadelphia, PA & The American Ornithologists' Union, Washington, D.C.
  • Erratum:
  • Orta, Jaume (1992a): 12. Pelagic Cormorant. In: del Hoyo, Josep; Elliott, Andrew & Sargatal, Jordi (eds.): Handbook of Birds of the World (Volume 1: Ostrich to Ducks): 346, plate 22. Lynx Edicions, Barcelona.
  • Orta, Jaume (1992b): Family Phalacrocoracidae (Cormorants). In: del Hoyo, Josep; Elliott, Andrew & Sargatal, Jordi (eds.): Handbook of Birds of the World (Volume 1: Ostrich to Ducks): 326–353, plates 22–23. Lynx Edicions, Barcelona.
  • SORA link
  • Woodhouse, S.C. (1910): English-Greek Dictionary – A Vocabulary of the Attic Language. George Routledge & Sons Ltd., Broadway House, Ludgate Hill, E.C.