Common and Roseate Terns high overhead

Common Tern (left) and Roseate Tern (right), adults in breeding plumage as seen high overhead on a sunny day. Illustration © David Sibley.

I was fortunate to be able to spend ten days in mid May 2021 on Great Gull Island, an American Museum of Natural History research site at the eastern end of Long Island Sound, New York. The island is occupied in summer by a very large colony of Common and Roseate Terns (among the largest colonies in the world of either species), and I was able to study thousands of Common Terns and hundreds of Roseate Terns every day.

Terns are overhead twenty-four hours a day, and both species perform elaborate and very elegant flight displays, sometimes hundreds of feet above the island. I thought those birds, with the translucent white feathers of their wings and tail lit up by the morning sun, were particularly beautiful, and I worked on some sketches of their shapes and patterns. In this illustration I was focused on comparing the differences between the species.

Both species have a deeply forked tail with long streamer-like outer tail feathers (especially long on Roseate Tern). One thing I found interesting in this study is that the “fork” at the tip of the tail is formed by the crossing of the outer tail feathers. Instead of a V-shaped tail these two birds have an X-shaped tail.

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