Spot the tern that’s not a Common Tern. Easy enough; yes? Now take a close look at the Common Terns.
These photos were taken on Pico in the Azores.
Do they look a little larger headed to you? A bit more elongated perhaps? Thicker, longer billed? Does the black on the bill look a little more extensive than our home grown Common Terns? I think it does.
Although The Azores are within the Western Palearctic these terns are reported to winter off the South American coasts of Brazil and Argentina, as do the Common Terns that breed in North America. From genetic studies the race of Common Tern in the States is proven to be the same race as in Europe.
The Common Terns on the Azores are not reported to be a separate race … but to my eye look structurally different.