Thalasseus maximus (Boddaert, 1783)

Species Naming

This species is the royal tern, with the scientific name Thalasseus maximus (Boddaert, 1783).

General Size Comparison

It is a large tern; among terns in the Americas, it is second only in size to the Caspian tern.

Similarity to Caspian Tern

It is unlikely to be confused with the Caspian tern, often called the "carrot-billed" giant, which has extensive dark underwing patches.

Wingspan

For adult royal terns of both sexes, average wingspan is 130 cm (51 in), with a range of 125–135 cm (49–53 in).

Length and Weight

Total length from bill to tail ranges from 45–50 cm (18–20 in), and body weight ranges from 350–500 g (12–18 oz).

Size Comparison to Related Terns

Two related species, the Old World West African crested tern (T. albididorsalis) and the greater crested tern (T. bergii), are the same size as the royal tern.

Distinction from West African Crested Tern

Vagrant royal terns in Europe require careful documentation to distinguish them from the West African crested tern, which has also been recorded in Europe.

Distinction from Elegant Tern

The royal tern may also be confused with the smaller elegant tern (T. elegans); the elegant tern has a longer but more slender, slightly downcurved bill, and a longer crest.

Adult Plumage and Bill

The royal tern has a stout orange-red bill, pale silvery-gray upperparts, and white underparts.

Leg Color

Its legs are black.

Breeding Season Crown and Crest

During spring, at the time of courtship and the start of the breeding season, the entire crown of the royal tern is black, with a shaggy, erectable crest on the nape.

Non-Breeding Plumage Pattern

From early summer into late winter, the black coloration first becomes patchy, then the forehead and upper crown turn fully white, with black retained only on the nape.

Molt Timing Compared to Elegant Tern

For northern populations, the royal tern's molt out of breeding plumage happens about two months earlier than the elegant tern's — in June, compared to August for the elegant tern — and results in more extensive white plumage on the head.

Juvenile Plumage

Juvenile royal terns are similar to non-breeding adults, but differ in having darker gray to blackish markings on the wings, and a yellower bill.

General Call Characteristics

The calls of the royal tern are usually short, clear shrills.

Specific Call Types

Some of these shrills sound like kree or tsirr; the species also produces a longer, rolling, more melodious plover-like whistle.

Overall Distribution

The royal tern is found on both coasts of the Americas.

Northeastern Breeding Range

In the northeastern part of its range, during the breeding season (April to July), it occurs primarily from Texas to Virginia, with scattered breeding records as far north as Long Island, New York, and as far south as French Guiana, on several Caribbean islands.

Southeastern Breeding Range

It also breeds in the southeastern part of its range, from southeastern Brazil south to Chubut Province in Argentina.

Eastern Americas Winter Range

In the eastern part of the Americas, the royal tern's wintering range extends from North Carolina south to Panama, the Guianas, and throughout the Caribbean.

Western Population Range

The western population of royal terns nests from California to Mexico and winters from California south to Peru.

Argentine Population Movement

Royal terns that breed in Argentina are resident or disperse into Brazil.