Phaetusa simplex
Silhouette: terngirl · PhyloPic
In 3 days ~20% in a week ~30%
The large-billed tern (Phaetusa simplex) is a species of tern in the family Laridae. It is placed the monotypic genus Phaetusa. It is found in most of South America (east of the Andes and north of the Pampas). It has occurred as a vagrant in Aruba, Bermuda, Cuba, Panama and the United States. Its natural habitats are rivers and freshwater lakes.
The large-billed tern was formally described in 1789 by the German naturalist Johann Friedrich Gmelin in his revised and expanded edition of Carl Linnaeus's Systema Naturae. He placed it with the other terns in the genus Sterna and coined the binomial name Sterna simplex. Gmelin based his description on the "simple tern" that had been described in 1785 by the English ornithologist John Latham in his book A General Synopsis of Birds from a specimen that had been collected in Cayenne, French Guiana. The large-billed tern is now the only species placed in the genus Phaetusa that was introduced for the species in 1832 by the German naturalist Johann Georg Wagler. The genus name comes from Greek mythology. Phaetusa (or Heliades) was sister to Phaethon and one of the daughters of Phoebus (Helios) and Clymene. The specific epithet simplex... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Parque Estadual Encontro das Águas | 🇧🇷 Brazil | |
| 2 | Anavilhanas National Park | 🇧🇷 Brazil | |
| 3 | Amacayacu National Natural Park | 🇨🇴 Colombia | |
| 4 | Iberá National Park | 🇦🇷 Argentina | |
| 5 | Tambopata National Reserve | 🇵🇪 Peru | |
| 6 | Cuyabeno Wildlife Reserve | 🇪🇨 Ecuador | |
| 7 | Manu National Park | 🇵🇪 Peru | |
| 8 | Caroni Swamp | 🇹🇹 Trinidad and Tobago | |
| 9 | El Palmar National Park | 🇦🇷 Argentina | |
| 10 | El Impenetrable National Park | 🇦🇷 Argentina | |
| 11 | Yasuní National Park | 🇪🇨 Ecuador | |
| 12 | Sierra de la Macarena National Park | 🇨🇴 Colombia | |
| 13 | Tayrona National Natural Park | 🇨🇴 Colombia |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Barranquilla | 🇨🇴 Colombia | |
| 2 | São Luís | 🇧🇷 Brazil | |
| 3 | Santa Cruz de la Sierra | 🇧🇴 Bolivia | |
| 4 | Asuncion | 🇵🇾 Paraguay | |
| 5 | Belém | 🇧🇷 Brazil | |
| 6 | Manaus | 🇧🇷 Brazil | |
| 7 | Porto Alegre | 🇧🇷 Brazil | |
| 8 | Valencia | 🇻🇪 Venezuela | |
| 9 | Caracas | 🇻🇪 Venezuela | |
| 10 | Bogota | 🇨🇴 Colombia |
With luck
About 10% of wildlife watchers report a Large-billed Tern sighting in El Impenetrable National Park on a given day, based on 20 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 170th most-seen of the 219 birds we can rate there. Over three days the chance rises to about 20%, and over a week to about 30%, if each day is a fresh chance.
October
In that month about 20% of wildlife watchers report a Large-billed Tern in El Impenetrable National Park on a given day, against under 5% in January to September, the lowest months. December has too few records to rate.
Between 8 and 11 am
Across all the parks we cover, that three-hour window holds the most Large-billed Tern sightings with a recorded time, and about 9 in 10 of them come between 6 am and 6 pm: it is a daytime animal.
10th of 13
Of the 13 parks where we can rate Large-billed Tern sightings, El Impenetrable National Park ranks 10th at about 10%. The best odds are in Parque Estadual Encontro das Águas (Brazil, about 70%), Anavilhanas National Park (Brazil, about 30%) and Amacayacu National Natural Park (Colombia, about 20%). All parks ranked.
Same family: Laridae
The closest relatives of the Large-billed Tern that you can see in El Impenetrable National Park (family Laridae, Gulls, Terns, and Skimmers) are Yellow-billed Tern (about 10%) and Black Skimmer (about 10%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Large-billed Tern is recorded against all the birds logged in El Impenetrable National Park (20 verified sightings from 2019 to 2026), calibrated against known sighting rates. Figures are rounded to the nearest 10% because citizen-science data supports honest approximations, not decimals, and months with records from fewer than five people show "—". How it works.
