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The Inca tern (Larosterna inca) is a near-threatened species of tern in the subfamily Sterninae of the family Laridae (the gulls, terns, and skimmers).<ref name=IOC13.1>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref name=IUCN/> It is found along the Pacific coasts of Chile, Ecuador and Perú,<ref name="SACCcountries">Remsen, J. V., Jr., J. I. Areta, E. Bonaccorso, S. Claramunt, A. Jaramillo, D. F. Lane, J. F. Pacheco, M. B. Robbins, F. G. Stiles, and K. J. Zimmer. 30 January 2023. Species Lists of Birds for South American Countries and Territories. https://www.museum.lsu.edu/~Remsen/SACCCountryLists.htm retrieved January 30, 2023</ref> and has appeared as a vagrant in Central America and Hawaii.<ref name=63Supp>R. Terry Chesser, Shawn M. Billerman, Kevin J. Burns, Carla Cicero, Jon L. Dunn, Blanca E. Hernández-Baños, Rosa Alicia Jiménez, Andrew W. Kratter, Nicholas A. Mason, Pamela C. Rasmussen, J. V. Remsen, Jr., Douglas F. Stotz, and Kevin Winker. "Sixty-third supplement to the American Ornithological Society's Check-list of North American Birds". American Ornithology 2022, vol. 139:1-13 retrieved August 9, 2022</ref>

Taxonomy and systematicsEdit

The Inca tern is the sole member of its monotypic genus Larosterna, and has no accepted subspecies.<ref name=IOC13.1/> Perhaps surprisingly given its highly distinct plumage, the Inca tern is not particularly basal among the terns, being more closely related to typical Sterna terns than any of the superficially much more similar genera Gelochelidon, Hydroprogne, Onychoprion, Phaetusa, or Sternula are.<ref>Template:Cite journal</ref><ref>Template:Cite journal</ref>

DescriptionEdit

File:Larosterna inca -Lima, Peru -family-8.jpg
Two adults and a juvenile (left) in Lima, Perú.

The Inca tern is roughly Template:Convert long and weighs between Template:Convert. Its plumage is uniquely colored among terns; adults have a mostly dark, slate-gray body, with paler underwing coverts, and a slightly paler throat. A white stripe extends back from the base of the bill and fans out like a Salvador Dalíesque mustache as long, satiny feathers along the side of the neck. The trailing edge of the wing (the tips of the secondaries and the three inner primaries) are white. The tail is black, and moderately forked. The iris is brown, with legs and feet that are dark red. The bill is bright to dark red, with bare yellow skin at the base. The chicks, on hatching, are purplish-brown, progressing through brownish-gray before developing mature plumage. The chicks' bills and legs are dark and horn-colored, and gradually attain the red that adults have.<ref name=INTE-BOW>Gochfeld, M. and J. Burger (2020). Inca Tern (Larosterna inca), version 1.0. In Birds of the World (J. del Hoyo, A. Elliott, J. Sargatal, D. A. Christie, and E. de Juana, Editors). Cornell Lab of Ornithology, Ithaca, NY, USA. https://doi.org/10.2173/bow.incter1.01 retrieved February 17, 2023</ref><ref name=Harrison>Template:Cite book</ref>

Distribution and habitatEdit

The Inca tern is an inhabitant of the Humboldt Current region. It breeds from Lobos de Tierra, in northern Perú, south to the Aconcagua River, near Valparaíso, Chile. Some disperse north into Ecuador after breeding,<ref name=INTE-BOW/><ref name=SACCcountries/> and south to the Puerto Montt area of Chile, where multiple 'research-grade' sightings with photos on the biodiversity database iNaturalist,<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> including a group of four together.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> It is a casual visitor to Panamá and Costa Rica, and has also been recorded as a vagrant in Guatemala and Hawaii.<ref name=63Supp/> The documented Hawaiian birds, in particular, remained from March through November on the Hawaiian archipelago.<ref name=63Supp/>

The South American Classification Committee of the American Ornithological Society treats the Inca tern's presence in Colombia as "hypothetical", due to a number of unverified or undocumented sightings.<ref name="SACCcountries" /> On iNaturalist, one 'research-grade' sighting (with photo) has been documented from the coast of Buenaventura, Colombia's Isla Cascajal, dated July 2023;<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref> however, the species' popularity in captivity (see Captivity below) complicates assessment of extralimital records.

The Inca tern nests on sea cliffs and guano islands, as well as manmade structures (such as ledges under piers) and abandoned barges. It will gather with other sea and shorebirds on sandy beaches.<ref name=INTE-BOW/><ref name=Harrison/>

BehaviorEdit

File:15-Islas Ballestas-nX-40.jpg
Large flocks may occur where conditions are suitable, as here on the Islas Ballestas off the Peruvian coast

MovementEdit

The Inca tern is essentially non-migratory, although some disperse northwards after breeding. Some rogue individuals have flown great distances.<ref name=INTE-BOW/>

FeedingEdit

The Inca tern feeds primarily on small fish, such as anchoveta (Engraulis ringens), and also consumes planktonic crustaceans and offal or carrion in its diet. Large flocks congregate around fishing boats and will also follow the feeding patterns of cormorants, sea lions, and whales and dolphins. Feeding flocks can number over 5,000 birds. The Inca tern catches its prey mainly by plunge-diving, but also picks items from the surface while flying or floating on the water.<ref name=INTE-BOW/><ref name=Harrison/>

BreedingEdit

Breeding does not appear to be concentrated in any season. Eggs have been found between April and July and between October and December, and other evidence of breeding has been noted in August. It nests in a variety of sites including fissures and caves in rock cliffs, among rocks and boulders on island slopes, in abandoned petrel and penguin burrows, and on and under human structures. The clutch size is usually two eggs though sometimes one. Both sexes incubate the clutch and provision the young. The incubation period is not known; fledging occurs about four weeks after hatch and the young are fully dependent on the adults for at least a month after fledging.<ref name=INTE-BOW/>

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VocalizationEdit

The Inca tern is most vocal at its nesting colonies. Its calls include "raucous cackling notes" and "mewing"; the latter call has been likened to that of a kitten.<ref name=INTE-BOW/><ref name=Harrison/>

StatusEdit

The IUCN has assessed the Inca tern as Near Threatened. It has a somewhat restricted range; its population size is not known and is believed to be decreasing. "Reproductive success is dramatically reduced during El Niño events". Human harvesting of its primary prey is a probable threat as is climate change.<ref name=IUCN/> One estimate placed its population at about 150,000 in 2011.<ref name=INTE-BOW/>

CaptivityEdit

Because of its unusual plumage, the species is popular in zoos. Escapes from captivity can occur, which leads to problems determining genuine vagrancy.<ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref><ref>{{#invoke:citation/CS1|citation |CitationClass=web }}</ref>

ReferencesEdit

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