Thalasseus bergii
Silhouette: JJ Harrison (vectorized by T. Michael Keesey) · PhyloPic
In 3 days ~70% in a week >90%
The greater crested tern (Thalasseus bergii), also called crested tern, swift tern, or great crested tern, is a tern in the family Laridae that nests in dense colonies on coastlines and islands in the tropical and subtropical Old World. Its four or five subspecies breed in the area from South Africa around the Indian Ocean to the central Pacific and Australia, all populations dispersing widely from the breeding range after nesting. This large tern is closely related to other species in its genus, but can be distinguished by its darker, battleship-grey upperparts, white forehead even in full breeding plumage, and greenish-tinged yellow (not orange or black) bill colour.
The greater crested tern has dark grey upperparts, white underparts, a yellow bill, and a shaggy black crest that recedes in winter. Its young have a distinctive appearance, with strongly patterned grey, brown and white plumage, and rely on their parents for food for several months after they have fledged. Like all members of the genus Thalasseus, the greater crested tern feeds by plunge diving for fish, usually in marine environments; the male offers fish to the female as part of the courtship ritual.
This is an adaptable species that has learned to follow fishing boats for jettisoned bycatch, and to use unusual nest sites such as the roofs of buildings and artificial islands in salt pans and sewage works. Its eggs and young are taken by gulls and ibises, and human activities such as fishing, shooting and egg harvesting have caused local population declines. There are no global conservation concerns for this bird, which has a stable total population of more than 500,000 individuals. Wikipedia →
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Zanzibar City | 🇹🇿 Tanzania | |
| 2 | Kozhikode | 🇮🇳 India | |
| 3 | Durban | 🇿🇦 South Africa | |
| 4 | Denpasar | 🇮🇩 Indonesia | |
| 5 | Kuwait City | 🇰🇼 Kuwait | |
| 6 | Perth | 🇦🇺 Australia | |
| 7 | Sydney | 🇦🇺 Australia | |
| 8 | Kollam | 🇮🇳 India | |
| 9 | Melbourne | 🇦🇺 Australia | |
| 10 | Davao City | 🇵🇭 Philippines |
| # | Zoo / Centre | Country | |
|---|---|---|---|
| 1 | Currumbin Wildlife Sanctuary | 🇦🇺 Australia | |
| 2 | Southern African Foundation for the Conservation of Coastal Birds | 🇿🇦 South Africa |
Likely
About 40% of wildlife watchers report a Crested Tern sighting in Cape Range on a given day, based on 92 verified sightings from GBIF citizen-science data from 2019 to 2026. It is the 16th most-seen of the 84 birds we can rate there. Over three days the chance rises to about 70%, and over a week to over 90%, if each day is a fresh chance.
March
In that month about 50% of wildlife watchers report a Crested Tern in Cape Range on a given day, against about 30% in August–October and December–January, the lowest months. That is one of Cape Range's wettest months, with about 40 mm of rain against almost none in October. February has too few records to rate.
Between 8 and 11 am
Across all the parks we cover, that three-hour window holds the most Crested Tern sightings with a recorded time, and nearly all of them come between 6 am and 6 pm: it is a daytime animal.
7th of 25
Of the 25 parks where we can rate Crested Tern sightings, Cape Range ranks 7th at about 40%. The best odds are in Rottnest Island (Australia, about 90%), Komodo National Park (Indonesia, about 60%) and Ningaloo Marine Park (Australia, about 50%). All parks ranked.
GBIF citizen-science records
It is estimated from how often the Crested Tern is recorded against all the birds logged in Cape Range (92 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.
