Caspian Tern

Fascinating facts about the Caspian Tern

• At up to 60 km (37 mi) from its nesting site, this tern will chase fish, showing a foraging range that rivals many seabirds and proves its willingness to travel far for a meal. That distance is the length of a marathon-plus-a-half, underscoring its role as a mobile link between inland lakes and coastal waters.
• Measuring 48–60 cm in length with a 127–145 cm wingspan, it outranks every other tern, making it as long as a school ruler and its wings as wide as a small adult’s outstretched arms. Its size gives it a commanding presence on the water, reminding us that size can evolve even in groups known for slenderness.
• A single clutch holds one to three pale blue-green eggs, each marked with heavy brown spots, and the parents incubate them for 26–28 days.
• After 35–45 days the fledglings leave the nest. Their varied plumage, from creamy to grey-brown, assists adults in recognizing their own chick.
• In 2016 a pair nested at Cape Krusenstern National Monument, Alaska, 600 km north of any previous North American breeding site, setting a new record. This poleward leap highlights how climate change can reshape even the most remote breeding frontiers.

At a glance

About the Caspian Tern

The Caspian tern (Hydroprogne caspia) commands attention as the world’s largest tern, stretching 48–60 cm in length with a wingspan of 127–145 cm and weighing up to 782 g. Its striking profile features a crisp white head capped by a permanent black crown, a long thick red-orange bill tipped in black, and black legs. In flight the bird’s pale grey back and underwings flash against dark primary feathers, while the tail remains only modestly forked, a subtle cue that sets it apart from its slimmer-tailed relatives. Throughout the year the black cap persists, gaining a faint white streak on the forehead in winter, and its call, a resonant, heron-like croak, echoes over the water where it hunts. Breeding colonies dot the great lakes of North America, the Baltic and Black Sea coasts of Europe, and remote shores of Asia, Africa, Australia and New Zealand. These terns plunge from hovering heights to snatch fish, sometimes travelling 60 km from the nest, and will opportunistically seize large insects, other birds’ eggs, or small rodents. They lay one to three pale blue-green, heavily speckled eggs on ground nests of gravel, sand, or low vegetation, incubating them for 26–28 days. Chicks, born in a spectrum from creamy to grey-brown, are recognized by parents thanks to this plumage variation, and they fledge after 35–45 days. A surprising note in their recent history: in 2016 a pair nested at Cape Krusenstern National Monument in northwestern Alaska, 600 km north of any prior North American record, a clear signal of the northward shift that climate warming is prompting in many seabirds.

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