This section is from the book "The Bird Book", by Chester A. Reed. Also available from Amazon: The Bird Book.
Gulls are webbed footed birds having a slight hook to the end of the upper mandible. Their plumage is generally a silvery gray above and white below. They nest in large colonies, some on the islands of fresh water inland, but mostly on the sea coast. They procure their food from the surface of the water, it consisting mostly of dead fish and refuse matter, and crustacea which they gather from the waters edge. When tired they rest upon the surface of the water, where they ride the largest waves in perfect safety.
Terns are birds of similar plumage to the Gulls, but their forms are less robust and the bills are generally longer and sharply pointed. Their food consists chiefly of small fish which they secure by hovering above the water, and then plunging upon them. They are less often seen on the surface of the water than are the Gulls.
Walter Raine. Characteristic Nest Of A Loon.