The southern black-backed gull. NZ

The southern black-backed gull (or ‘black-back’) is one of the most abundant and familiar large birds in New Zealand, although many people do not realise that the mottled brown juveniles (mistakenly called “mollyhawks”) are the same species as the immaculate adults. Found on or over all non-forested habitats from coastal waters to high-country farms, this is the only large gull found in New Zealand. They are particularly abundant at landfills, around ports and at fish-processing plants...Known widely as ‘kelp gull’ in other countries, the same species is also common in similar latitudes around the southern hemisphere, including southern Australia, South America, southern Africa, and most subantarctic and peri-Antarctic islands, and the Antarctic Peninsula...The familiar large gull throughout New Zealand. Adults have white head and underparts with black back, yellow bill with red spot near tip of lower mandible, and pale green legs. Juveniles are dark mottled brown with black bill and legs; their plumage lightens with age until they moult into adult plumage at 3 years old.