Like many species of bird, the name "Common" doesn't always mean it's the most common form to be found. In my experience, the Sandwich Tern seems far more common on the north-east coast. From a distance it's not always easy to tell the terns apart. They have different calls, sizes, tail shapes etc, but I've found the best way to distinguish them is the bill colouration. Common Terms have a long bright red bill with an obvious black tip. The other similar term in the Arctic Tern, and their bill is all over red, and appears a little shorter than the common tern's.
