Caspian Tern

The Caspian tern, known scientifically as Hydroprogne caspia, stands as the largest tern in the world. It boasts a considerable size, measuring 48–60 cm in length, with a wingspan stretching 127–145 cm, and tipping the scales at 530–782 g. The adult Caspian tern is distinguished by its black legs and a robust red-orange bill, tipped with a hint of black. Its plumage is a study in contrast, with a white head, neck, belly, and tail, set against a black cap and pale grey upper wings and back. The underwings are pale, but the primary feathers are dark. When observed in flight, the tail appears less forked compared to other terns, and the wingtips reveal a black underside.

Identification Tips

To identify the Caspian tern, look for its long, thick bill colored in vibrant red-orange with a small black tip. In flight, note the less forked tail and the distinctive black on the underside of the wingtips. During the non-breeding season, the black cap remains, but may show white streaking on the forehead.

Habitat

The Caspian tern favors large lakes and ocean coasts for its breeding grounds. These locations span across North America, including the Great Lakes, parts of Europe around the Baltic and Black Seas, as well as select regions in Asia, Africa, and Australasia.

Distribution

This species has a subcosmopolitan but scattered distribution. In North America, the birds migrate to southern coasts, the West Indies, and northern South America. European and Asian populations spend the non-breeding season in the Old World tropics, while African and Australasian birds tend to be resident or only disperse short distances.

Behaviour

The Caspian tern is known for its feeding flights, which can extend up to 60 km from the breeding colony. It primarily feeds on fish, diving after hovering high above the water. Occasionally, it may also consume large insects, the young and eggs of other birds, and even rodents.

Song & Calls

The vocalizations of the Caspian tern are reminiscent of a loud heron-like croak, a distinctive sound that can be heard over the waters where it hunts and dwells.

Breeding

The breeding season occurs in spring and summer, with the tern laying one to three pale blue-green eggs, heavily spotted with brown. Nesting can be a solitary affair or within colonies, often alongside other tern and gull species. The nests are typically situated on the ground among gravel and sand or sometimes on vegetation. Incubation takes 26–28 days, and the chicks exhibit variable plumage patterns, aiding parents in identifying their offspring. Fledging is achieved after 35–45 days.

Similar Species

While the Caspian tern is unique in its size and bill coloration, it may be confused with other large terns. However, its distinctive features, particularly the bill and less forked tail, usually allow for accurate identification.

Diet and Feeding

The Caspian tern's diet is predominantly fish, which it skillfully captures through aerial dives. Its foraging can take it over considerable distances, and it is not uncommon to see it fishing in freshwater lakes as well as marine environments.

Conservation status

The Caspian tern is currently listed as Least Concern on the IUCN Red List. The global population is estimated at around 50,000 pairs, with most regional populations remaining stable. However, the population in the Baltic Sea is experiencing a decline and is a focus of conservation efforts. The species is also protected under the Agreement on the Conservation of African-Eurasian Migratory Waterbirds (AEWA).