This is a large tern, second only to Caspian tern but is unlikely to be confused with the carrot-billed giant, which has extensive dark under wing patches.

The royal tern has an orange-red bill, pale grey upper parts and white under parts.
Its legs are black.
In winter, the black cap becomes patchy.
Juvenile royal terns are similar to non-breeding adults.
Differences include juveniles having black splotched wings and a yellower bill.
An adult royal tern has an average wingspan of 130 cm (51 in), for both sexes, but their wingspan can range from 125–135 cm (49–53 in).
The royal tern's length ranges from 45–50 cm (18–20 in) and their average weight is anywhere from 350–450 g (12–16 oz).

The calls of the royal tern are usually short, clear shrills.
Some of the shrills sound like kree or tsirr; the royal tern also has a more plover like whistle that is longer, rolling and is more melodious.

In various parts of its range, the royal tern could be confused with the elegant tern, lesser crested tern (the other orange-billed terns), and the greater crested tern.
It is paler above than lesser crested tern and the yellow-billed great crested tern.
The elegant tern has a longer more curved bill and shows more white on the forehead in winter.
This is a large tern, second only to Caspian tern but is unlikely to be confused with the carrot-billed giant, which has extensive dark under wing patches.
The royal tern has an orange-red bill, pale grey upper parts and white under parts. Its legs are black. In winter, the black cap becomes patchy. Juvenile royal terns are similar to non-breeding adults. Differences include juveniles having black splotched wings and a yellower bill. An adult royal tern has an average wingspan of 130 cm (51 in), for both sexes, but their wingspan can range from 125–135 cm (49–53 in). The royal tern's length ranges from 45–50 cm (18–20 in) and their average weight is anywhere from 350–450 g (12–16 oz).
The calls of the royal tern are usually short, clear shrills. Some of the shrills sound like kree or tsirr; the royal tern also has a more plover like whistle that is longer, rolling and is more melodious.
In various parts of its range, the royal tern could be confused with the elegant tern, lesser crested tern (the other orange-billed terns), and the greater crested tern. It is paler above than lesser crested tern and the yellow-billed great crested tern. The elegant tern has a longer more curved bill and shows more white on the forehead in winter.
Royal tern