| Inca tern | |
|---|---|
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| Inca tern atLima, Peru | |
Scientific classification | |
| Domain: | Eukaryota |
| Kingdom: | Animalia |
| Phylum: | Chordata |
| Class: | Aves |
| Order: | Charadriiformes |
| Family: | Laridae |
| Genus: | Larosterna Blyth, 1852 |
| Species: | L. inca |
| Binomial name | |
| Larosterna inca | |
 | |
| Range ofL. inca Year-round range Non-breeding range | |
The Inca tern (Larosterna inca) is anear-threatened species oftern in the subfamilySterninae of the familyLaridae (thegulls, terns, andskimmers).[2][1] It is found along thePacific coasts ofChile,Ecuador andPerú,[3] and has appeared as avagrant inCentral America andHawaii.[4]
The Inca tern is the sole member of its monotypic genusLarosterna, and has no accepted subspecies.[2] Perhaps surprisingly given its highly distinct plumage, the Inca tern is not particularlybasal among the terns, being more closely related to typicalSterna terns than any of the superficially much more similar generaGelochelidon,Hydroprogne,Onychoprion,Phaetusa, orSternula are.[5][6]
The Inca tern is roughly 39 to 42 cm (15 to 17 in) long and weighs between 180 to 210 g (6.3 to 7.4 oz). Its plumage is uniquely colored among terns; adults have a mostly dark, slate-gray body, with paler underwingcoverts, and a slightly paler throat. A white stripe extends back from the base of the bill and fans out like aSalvador Dalíesquemustache as long, satiny feathers along the side of the neck. The trailing edge of the wing (the tips of the secondaries and the three innerprimaries) 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.[7][8]
The Inca tern is an inhabitant of theHumboldt Current region. It breeds fromLobos de Tierra, in northern Perú, south to theAconcagua River, nearValparaíso, Chile. Some disperse north into Ecuador after breeding,[7][3] and south to thePuerto Montt area of Chile, where multiple 'research-grade' sightings with photos on thebiodiversity databaseiNaturalist,[9] including a group of four together.[10] It is a casual visitor toPanamá andCosta Rica, and has also been recorded as avagrant inGuatemala and Hawaii.[4] The documented Hawaiian birds, in particular, remained from March through November on theHawaiian archipelago.[4]
The South American Classification Committee of theAmerican Ornithological Society treats the Inca tern's presence inColombia as "hypothetical", due to a number of unverified or undocumented sightings.[3] On iNaturalist, one 'research-grade' sighting (with photo) has been documented from the coast ofBuenaventura, Colombia's Isla Cascajal, dated July 2023;[11] however, the species' popularity in captivity (seeCaptivity below) complicates assessment of extralimital records.
The Inca tern nests onsea cliffs andguano 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.[7][8]
The Inca tern is essentially non-migratory, although some disperse northwards after breeding. Some rogue individuals have flown great distances.[7]
The Inca tern feeds primarily on small fish, such asanchoveta (Engraulis ringens), and also consumesplanktoniccrustaceans andoffal orcarrion in its diet. Large flocks congregate around fishing boats and will also follow the feeding patterns ofcormorants,sea lions, andwhales anddolphins. Feeding flocks can number over 5,000 birds. The Inca tern catches its prey mainly byplunge-diving, but also picks items from the surface while flying or floating on the water.[7][8]
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.[7]
| Songs and calls |
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.[7][8]
TheIUCN 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 duringEl Niño events". Human harvesting of its primary prey is a probable threat as is climate change.[1] One estimate placed its population at about 150,000 in 2011.[7]
Because of its unusual plumage, the species is popular inzoos. Escapes from captivity can occur, which leads to problems determining genuine vagrancy.[12][13]
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