Nomad

Nomad (Vampire)
Nomadic vampires are vampires with no permanent residence. Nomads are always or nearly always "normal" vampires according to diet, drinking human blood as opposed to the "vegetarian" diet of the The Cullens and the Denali Coven. In fact, their diet is the very thing that causes them to be nomads, as they cannot stay in one place for too long. The authorities would probably become suspicious if there were too many deaths, all in the same manner, in one place in one year or so, and at fairly regular intervals, too.

Twilight
The first example of nomadic vampires appears in Twilight with James, Victoria, and Laurent. James' coven are nomads who are constantly on the move as a result of their diet. Since they drink human blood, James begins to hunt Bella, partially as a result of Edward's defense of her in the meadow where the Cullen clan had been playing baseball ("it's the American pastime," as Edward says), partially as a result of how very "tempting" her blood allegedy smells to vampires.

New Moon
There are few references to nomads in New Moon, as Edward is gone for much of the book, resulting in most of the Forks action taking place in werewolf culture as opposed to vampire. Since the rest of the plotline takes place in Volterra, where the Volturi have their stronghold (stronghold implies a permanent residence), the only action involving a nomadic coven occurs when Laurent, who has since moved to Denali (though he "cheats", as evidenced by his eyes, which remain red as opposed to the golden color that they would be if he had truly changed his dietary preferences) comes back to help Victoria avenge James ("mate for mate"; meaning that their target is Bella rather than Edward).

Eclipse
As in New Moon, there are virtually no references to nomadic vampires in Eclipse. Laurent is dead, and as Victoria is now to some extent making herself leader of a coven of newborns in Seattle--a somewhat permanent residence, there are really no references to nomadic vampires.