Onychoprion anaethetus
Silhouette: Sheatherius · PhyloPic
In 3 days ~80% in a week >90%
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 |
Likely
About 40% of wildlife watchers report a Bridled Tern sighting in Rottnest Island on a given day, based on 235 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 25th most-seen of the 81 birds we can rate there. Over three days the chance rises to about 80%, and over a week to over 90%, if each day is a fresh chance.
January and October–November
In those months about 60% of wildlife watchers report a Bridled Tern in Rottnest Island on a given day, against about 10% in July and August, the lowest months. Those are among Rottnest Island's driest months, with about 25 mm of rain a month against 120 mm in June.
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.
Yes
Of the 12 parks where we can rate Bridled Tern sightings, Rottnest Island has the highest daily chance: about 40%. Next come Komodo National Park (Indonesia, about 10%) and Raja Ampat (Indonesia, about 10%).
Same family: Laridae
The closest relatives of the Bridled Tern that you can see in Rottnest Island (family Laridae, Gulls, Terns, and Skimmers) are Silver Gull (over 90%), Crested Tern (about 90%) and Caspian Tern (about 70%), with each one's daily chance of a sighting.
GBIF citizen-science records
It is estimated from how often the Bridled Tern is recorded against all the birds logged in Rottnest Island (235 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.
