Onychoprion anaethetus
Silhouette: Sheatherius · PhyloPic
In 3 days <5% in a week ~10%
The bridled tern (Onychoprion anaethetus) is a seabird of the family Laridae. It is a bird of the tropical oceans. The scientific name is from Ancient Greek. The genus comes from onux meaning "claw" or "nail", and prion, meaning "saw". The specific anaethetus means "senseless, stupid", in reference to its tameness around humans.
This is a medium-sized tern, at 30–32 cm in length and with a 77–81 cm wingspan similar to the common tern in size, but more heavily built. The wings and deeply forked tail are long, and it has dark grey upperparts and white underparts. The forehead and eyebrows are white, as is a striking collar on the hindneck. It has black legs and bill. Juvenile bridled terns are scaly grey above and pale below.
This species is unlikely to be confused with any tern apart from the similarly dark-backed sooty tern and the spectacled tern from the Tropical Pacific. It is paler-backed than that sooty, (but not as pale as the grey-backed) and has a narrower white forehead and a pale neck collar.
This bird is migratory and dispersive, wintering more widely through the tropical oceans. It has markedly marine habits compared to... Wikipedia →
| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Rottnest Island | 🇦🇺 Australia | |
| 2 | Komodo National Park | 🇮🇩 Indonesia | |
| 3 | Raja Ampat | 🇮🇩 Indonesia | |
| 4 | Coiba National Park | 🇵🇦 Panama | |
| 5 | Ningaloo Marine Park | 🇦🇺 Australia | |
| 6 | Cape Range | 🇦🇺 Australia | |
| 7 | Yala National Park | 🇱🇰 Sri Lanka | |
| 8 | Manuel Antonio National Park | 🇨🇷 Costa Rica | |
| 9 | Cabo Blanco Absolute Nature Reserve | 🇨🇷 Costa Rica | |
| 10 | Corcovado National Park | 🇨🇷 Costa Rica | |
| 11 | Daintree National Park | 🇦🇺 Australia | |
| 12 | Bastimentos Island National Marine Park | 🇵🇦 Panama |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | Perth Zoo | 🇦🇺 Australia | |
| 2 | Caversham Wildlife Park | 🇦🇺 Australia |
Rare
Under 5% of wildlife watchers report a Bridled Tern sighting in Manuel Antonio National Park on a given day, based on 29 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 231st most-seen of the 325 birds we can rate there. Over three days the chance rises to under 5%, and over a week to about 10%, if each day is a fresh chance.
July and August
In those months about 10% of wildlife watchers report a Bridled Tern in Manuel Antonio National Park on a given day, against under 5% in September to June, the lowest months. Those are among Manuel Antonio National Park's wettest months, with about 700 mm of rain a month against 35 mm in February.
Between 10 am and 1 pm
Across all the parks we cover, that three-hour window holds the most Bridled 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.
8th of 12
Of the 12 parks where we can rate Bridled Tern sightings, Manuel Antonio National Park ranks 8th at under 5%. The best odds are in Rottnest Island (Australia, about 40%), Komodo National Park (Indonesia, about 10%) and Raja Ampat (Indonesia, about 10%).
GBIF citizen-science records
It is estimated from how often the Bridled Tern is recorded against all the birds logged in Manuel Antonio National Park (29 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.
