can you please describe the third bird that you mentioned?
A very large white gull with dark wings and back, and a very thick red-tipped yellow bill.
Pacific gull
Pacific gulls are the only large gulls in their range, besides the occasional kelp gull. This species can range in length from and span across the wings. They typically weigh from . This species is mostly white, with dark wings and back, and a very thick (when compared to other gull species), powerful, red-tipped yellow bill. 
what is a australasian gannet? A large seabird. where is it found? Steep Point in Western Australia, along the southern and eastern Australian coastline to the vicinity of Rockhampton in Queensland, as well as the North and South Islands of New Zealand, Lord Howe and Norfolk Islands. what does it eat? Forage fish and cephalopods. apart from this bird what are the other predators of the first one? Other fishes like tuna, striped bass, cod, salmon, barracuda and swordfish, as well as sharks, whales, dolphins, porpoises, seals, sea lions, and seabirds. where are they found? They are found along coastlines and also in lakes and rivers. does the original bird have a unique call? A  harsh "arrah-arrah" or "urrah-urrah". who are its predators? Southern giant petrel , kelp gull, and Pacific gull. how does the first one mate? It sexual maturity at six or seven years of age and the breeding season begins in October. what does it eat? Fish, krill, squid, offal , and waste from vessels. what is the sub-species of the second bird you mentioned? "L. d. dominicanus" and  "L. d. vetula" .
wiki:1900742
Pacific gull [SEP] Description
Pacific gulls are the only large gulls in their range, besides the occasional kelp gull. This species can range in length from and span across the wings. They typically weigh from . This species is mostly white, with dark wings and back, and a very thick (when compared to other gull species), powerful, red-tipped yellow bill. They have salt glands that secrete salty water through the nostrils. Young birds are mottled-brown all over, and attain their adult plumage only gradually; by its fourth year, a young Pacific gull has usually become difficult to tell apart from an adult bird. Of the two subspecies, the nominate eastern race prefers sheltered beaches, and the western race "L.