The Pacific Gull - Larus pacificus - is a large bird; adults are black and white with yellow legs and feet and a large red-tipped yellow bill. Juveniles have a dark coloured bill, iris and legs; body is largely dark brown, slightly mottled. Mature plumage is gained after six partial or full moults in three years so a wide variation in colouring is observable. At first, the body underside becomes lighter in colour, this progresses along the entire underside in successive moults while the underside of the wings changes to black and white and the upper wing surface becomes black with white trailing edge tips. Females are smaller with less massive bill. Grows 50 to 66 centimetres.
There are two versions. The eastern subspecies (pacificus) has a white iris; the western subspecies (georgii) has a red iris making the eye look dark from a distance (photograph above). Mount Gambier is the border between subspecies.