Caspian terns build a type of nest known as a scrape. It's typically a shallow depression lined with stones, shells and vegetation. (text and image from MNN)I love that image of the nest - it would be something I would make in a shallow bowl and put on my coffee table!
(Image from here)
The Caspian Tern is the largest of all terns and can be found in North America, Europe, Australia, New Zealand, Asia and Africa. Cornell's bird site has some more pictures along with the sound of this tern - you can find that here. Cornell's site is a wonderful resource for anyone interested in birds.
This book was one of my favorite finds when I was at summer camp in Nova Scotia as a teenager - it was and still is one of the cleverest things! And, of course, the tern makes an appearance.