Royal tern

The royal tern (Thalasseus maximus) is a tern in the family Laridae. The species is endemic to the Americas, though vagrants have been identified in Europe.

This is a large tern, second only to the Caspian tern among terns in the Americas, but is unlikely to be confused with this "carrot-billed" giant, which has extensive dark underwing patches. Adults have an average wingspan of 130 cm (51 in) for both sexes, with a range from 125–135 cm (49–53 in). Its bill-to-tail length ranges from 45–50 cm (18–20 in) and the weight is anywhere from 350–500 g (12–18 oz). The Old World West African crested tern T. albididorsalis and greater crested tern T. bergii are the same size; vagrant royal terns in Europe need careful documentation to distinguish them from the West African crested tern, which has also been recorded in Europe. The royal tern can also be confused with the smaller elegant tern T. elegans; that has a longer but slenderer, slightly downcurved, bill, and a longer crest.

The royal tern has a stout orange-red bill, pale silvery-gray upperparts, and white underparts. Its legs are black. The entire crown is black with a shaggy, erectable crest on the nape in the spring during courtship and the start of the breeding season. From early summer into late winter, the black becomes first patchy and then fully white on the forehead and upper crown, retaining black only on the nape. Compared to elegant tern, its molt out of breeding plumage is about two months earlier (June, versus August, for northern populations), and more extensively white. Juvenile royal terns are similar to non-breeding adults, differing in the juveniles having darker gray to blackish marks on the wings, and a yellower bill.

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