The Little Tern is one of the UK's rarer terns, but they do sometimes nest on the Northumberland coast at Long Nanny. As their name suggests, they are quite small, about half the size of a Sandwich Tern. The best place to see them is not the nesting site, as this is protected and they should not be disturbed. Good views can be had on the shoreline at low tide - Terns will fly out to sea to catch fish, then fly back to the nesting site, so you will get good views of them on the beach and out at sea. If you're really lucky you might see a little scene with two interacting in the shallows, like the photo below...

The characteristic feature is their bill, which is bright yellow with a black tip. Little Terns (like all terns) are very streamlined and elegant in flight. However, unlike most terns which have long forked tails, Little terns tend to have a closed narrow pointed tail as shown in the photo below, although they can sometimes spread it out into a fork.