Marine birds are a group of seabirds that live in or near the ocean. ERNS and ERNES are two species of marine birds. ERNS, also known as the Royal Tern, is a large seabird with a black cap, white forehead, and orange bill. It is found in tropical and subtropical regions around the world. ERNES, also known as the Black Tern, is a small seabird with a black head, white underparts, and a forked tail. It is found in temperate and subtropical regions around the world. Both species of marine birds feed on fish, crustaceans, and other aquatic animals.