Gelochelidon macrotarsa
In 3 days ~10% in a week ~30%
The Australian tern or Australian gull-billed tern (Gelochelidon macrotarsa) is a tern in the family Laridae, native to Australia. The genus name is from Ancient Greek gelao, "to laugh", and khelidon, "swallow". John Gould described Sterna macrotarsa from a specimen held at King's College, London in 1837. Although first described as a species, throughout most of the 20th and early 21st centuries it was generally considered to be a subspecies of the gull-billed tern, but was re-elevated to species status by the IOC World Bird List in 2019 in its Version 9.2.
This is a fairly large and powerful tern, similar in size and general appearance to a Sandwich tern, but the short thick gull-like bill, broad wings, long legs and robust body are distinctive. The summer adult has pale grey upperparts, white underparts, a black cap, strong black bill and black legs. The call is a characteristic ker-wik. It is 33–42 cm (13–17 in) in length and 76–91 cm (30–36 in) in wingspan. Its weight ranges from 150–292 g (5.3–10.3 oz). It differs from the closely related gull-billed tern in being slightly larger, paler grey above, and with an obviously larger, heavier bill.
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| # | Park | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Cape Range | 🇦🇺 Australia | |
| 2 | Ningaloo Marine Park | 🇦🇺 Australia | |
| 3 | Noosa National Park | 🇦🇺 Australia | |
| 4 | Kakadu National Park | 🇦🇺 Australia | |
| 5 | Daintree National Park | 🇦🇺 Australia |
| # | City | Country | Daily sighting probability |
|---|---|---|---|
| 1 | Brisbane | 🇦🇺 Australia |
Rare
Under 5% of wildlife watchers report an Australian Tern sighting in Brisbane on a given day, based on 763 verified sightings from GBIF citizen-science data. It is the 111th most-seen of the 237 birds we can rate there. Over three days the chance rises to about 10%, and over a week to about 30%, if each day is a fresh chance.
June to September
In those months about 10% of wildlife watchers report an Australian Tern in Brisbane on a given day, against under 5% in October to May, the lowest months. Those are among Brisbane's driest months, with about 50 mm of rain a month against 160 mm in February.
Between noon and 3 pm
Across all the parks we cover, that three-hour window holds the most Australian Tern sightings with a recorded time, and nearly all of them come between 6 am and 6 pm: it is a daytime animal.
Only Brisbane, in our data
Brisbane is the only city on Wallace's Line with enough records to rate Australian Tern sightings: under 5% of wildlife watchers there report one on a given day.
GBIF citizen-science records
It is estimated from how often the Australian Tern is recorded against all the birds logged in Brisbane (763 verified sightings), 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.
