The graceful roseate tern (Sterna dougallii) can typically be found along the eastern coast of the United States, as well other places with a similar climate throughout the world (France, Turkey, Japan, eastern China). Distinct from the common tern in their black bills during mating season and longer streaming tail feathers (a beautiful sight to behold!), the roseate tern is currently on the endangered species list, with less than 100,000 remaining in existence, and less than 1,000 on the eastern seaboard.
They generally breed in April, with eggs hatching in late May. They often live close to each other in large colonies to provide greater protection against enemies. One major reason for their population decline has been their low-laying nests, which prove to be easy prey for foxes, snakes, and other predators. After birth, a roseate chick generally takes about a month to fledge, and then will only stay in the nest for about a week before leaving with its parents to learn how to catch fish, its primary food source. One interesting fact to note is that roseate terns can actually "fly" under water for short distances to catch their prey. They commonly feed on sand lances, haddocks, and codfish.
Roseate terns, like other terns, are migratory birds, heading for more tropical climates during the winter months. It is believed that the younger terns (those less than two years old) remain in the winter areas of South America and Australia until they are confident enough to return to the breeding areas as mates themselves. One speculation suggests that in the months leading up to the breeding period, roseate terns become pelagic - that is, live on the ocean and do not come ashore - to increase their likelihood of survival.
The major threat to the roseate tern population is actually another seafaring bird: the gull. Gulls are much larger than terns and frequently perform hostile takovers of tern nests for their own purposes. They eat tern eggs and fledglings, and occasionally adult terns. However, there are often little alternatives for terns wishing to nest, as commercial land use is making suitable breeding grounds scarcer every year. Another major concern is the fish population that provides their food - commercial spillage and pollution have limited the numbers of fish in the inlet shores of Nova Scotia, New York, and other areas, which in turn limits the roseate's food supply.
A lovely painting by John Audubon of a roseate tern (made after he and his party killed 38 of them) can be found at http://www.floridakeysbest.com/audubon/roseate_tern.htm.