Sterna hirundo Linnaeus, 1758

Because the coloring of common terns changes significantly as seasons change, they are often difficult to identify from plumage alone. They are most easily identified by their black head and red bill. The tail is forked and the tail feathers are more elongated than those of most terns. The wings are pointed and the inner and outer parts of each wing are the same width. The body of common terns is whitish-gray and the underparts are much paler than the upperparts, particularly in adult terns. The female is usually smaller than the male, although only slightly. The bill is usually pointed downward when the tern flies. Other notable characteristics include an exceptionally powerful head and neck and unusually long legs, which distinguish them from other terns such as Arctic terns.