Large-billed Tern Phaetusa simplex Scientific name definitions

The Large-billed Tern is an unmistakable South American species, and the only member of the genus Phaetusa. The large, heavy bill and striking wing pattern with black primaries, white secondaries, and a gray back, make this bird visually distinctive. During the breeding season, this species can be found along broad, inland rivers and lakes, nesting on the sandy shores in mixed species colonies with Black Skimmers (Rynchops niger) and Yellow-billed Terns (Sternula superciliaris). During the nonbreeding season, some of the population congregates on the eastern coast of South America in coastal mangroves, beaches, and estuaries. Young birds are prized pets of Native Americans in certain parts of the Large-billed Tern’s range. Common throughout most of its range, the Large-billed Tern’s main threats are habitat disturbance and egg-collecting.

38–42 cm; 208–247 g. Unmistakable large, relatively short-tailed tern, with very heavy yellow bill, and striking wing pattern ; crown to ear-coverts black; upperparts medium grey (darker than in most terns), but secondaries and greater wing-coverts white ; lores and underparts white, sides of flanks tinged grey; iris blackish brown; legs and feet yellow. Conspicuous pattern in flight: black primaries, grey back and triangular white patch on secondaries and coverts, reminiscent of <em>Xema sabini</em> . Non-breeding adult  has crown and forehead paler. Juvenile has less black on crown; back and wings mottled with brown; bill  duller. Race chloropoda has slightly paler upperparts and brighter bill.

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Editor's Note: Additional distribution information for this taxon can be found in the 'Subspecies' article above. In the future we will develop a range-wide distribution article.

Occupies broad (and occasionally narrow) inland rivers and lakes, breeding on beaches and sandbars; has bred once on coast (Rio Grande do Sul). Non-breeders also frequent coastal mangroves, beaches and estuaries.

Winters on rivers and on coast. Common throughout year on Guianan coast, with smaller numbers May–Aug when breeding. Accidental in West Indies (Cuba, May 1909 (2 Ramsden, C.T. (1912). Phaetusa magnirostris Licht. in Cuba. Auk. 29(1): 100. Close ); Grenada, May/Jun 2010) (3 White, A. and Jeremiah, A. (2011). First record of Large-billed Tern (Phaetusa simplex) for Grenada and the Lesser Antilles. J. Carib. Orn.. 24(2): 74–76. Close ), on Aruba (May 1908) (4 Prins, T.G., Reuter, J.H., Debrot, A.O., Wattel, J. and Nijman, V. (2009). Checklist of the birds of Aruba, Curaçao and Bonaire, south Caribbean. Ardea. 97(2): 137–268. Close ), Bermuda (Jun 1961), Honduras (late Apr 2003) (5 Howell, S. N. G., I. Lewington, and W. Russell (2014). Rare Birds of North America. Princeton University Press, Princeton, NJ, USA. Close ), Costa Rica (mid-Mar 2003, mid-Jun 2007) (6 Sandoval, L., Sánchez, C., Biamonte, E., Zook, J.R., Sánchez, J.E., Martínez, D., Loth, D. and O’Donahoe, J. (2010). Recent records of new and rare bird species in Costa Rica. Bull. Brit. Orn. Club 13123(4): 237–245. Close ), Panama (multiple records from both sides of the Canal Zone) (7 Angehr, G. R., and R. Dean (2010). The Birds of Panama: A Field Guide. Cornell University Press, Ithaca, New York, USA. Close ), and USA (Illinois in mid-Jul 1949, Ohio in late May 1954, New Jersey in late May 1988) (5 Howell, S. N. G., I. Lewington, and W. Russell (2014). Rare Birds of North America. Princeton University Press, Princeton, NJ, USA. Close ). Considered only a visitor to Trinidad (late Jan–Nov), though occasionally breeds (8 Kenefick, M., Restall, R. and Hayes, F.E. (2011). Birds of Trinidad & Tobago. Second edn. Christopher Helm, London. Close ), with just one report from adjacent Tobago (9 ffrench, R. P., and M. Kenefick (2003). Verification of rare bird records from Trinidad and Tobago. Cotinga 19:75–78. Close ). In South America, also recorded W of Andes in NW Peru (Lambayeque, Jan 2012; Arequipa, Mar 2012) (10 Puse-Fernández, E. and Angulo Pratolongo, F. (2013). Large-billed Tern Phaetusa simplex west of the Peruvian Andes. Cotinga. 35: 116–117. Close , 11 Luque, C. and Tejada, C. (2013). Primer registro de Gaviotín de Pico Grande (Phaetusa simplex) en el Santuario Nacional Lagunas de Mejía y en la costa sur del Perú. Bol. UNOP. 8(1): 6–9. Close ) and in SW Ecuador (Mar 2015) (12 Williams, R. (2016). Neotropical notebook. Neotropical Birding. 18: 45–52. Close ).

Fish  4–12 cm long; also insects. Feeds mainly by plunge-diving from 6–11 m; also by contact-dipping (swooping c. 2 m over water), hover -dipping  , and occasionally skimming. Performs aerial hawking over mudflats, and follows plough (Surinam) to capture insects. Occasionally pirates food from conspecifics.

Raspy “kree” and “kew” notes, often given as a series (13 Schulenberg, T. S., D. F. Stotz, D. F. Lane, J. P. O’Neill, and T. A. Parker (2010). Birds of Peru. Revised edition. Princeton University Press, Princeton, New Jersey, USA. Close ).

May–Jun and Oct–Dec in N of range, Aug–Sept in Argentina. Nests  singly or in groups of up to 100 pairs, mainly on sandbars with Rynchops niger and Sternula superciliaris (14 Zarza, R., Cintra, R. and Anciães, M. (2013). Distribution, abundance and habitat selection by breeding Yellow-billed Terns (Sternula superciliaris), Large-billed Terns (Phaetusa simplex) and Black Skimmers (Rynchops niger) in the Brazilian Amazon. Waterbirds. 36(4): 470–481. Close ), as well as Sand-coloured Nighthawks (Chordeiles rupestris). Changes nest-sites from year to year. Usually no nest material. Up to three eggs  (mean 2·3). Few other published data. Productivity 1·66 young/nest. In Peru 68% of nests successful.

Not globally threatened (Least Concern). Very widespread E of Andes, and common along the length of R Orinoco. Available population estimates are rough guesses but nominate race may number 10,000–25,000 birds and race chloropoda is even more numerous (15 Wetlands International (2015). Waterbird Population Estimates. Wetlands International, Wageningen, The Netherlands. Close ). Species is decidedly rare in E Ecuador. Breeding beaches are frequently inundated, or subject to disturbance from humans or ungulates. Egg-collecting occurs, but unpredictability of colony locations and of breeding phenology mean that species is not currently threatened. Most nest failures are apparently due to flooding; adults and young sometimes eaten by boas (Constrictor constrictor).