who are its predators?
Southern giant petrel , kelp gull, and Pacific gull.
Australasian gannet
The southern giant petrel ("Macronectes giganteus") has been recorded preying on an adult Australasian gannet by holding it underwater and drowning it. Eggs and chicks can fall victim to the kelp gull ("Larus dominicanus") and Pacific gull ("Larus pacificus"), particularly if parent birds have been disturbed.
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".
wiki:6510553
Australasian gannet [SEP] Predators and parasites
The southern giant petrel ("Macronectes giganteus") has been recorded preying on an adult Australasian gannet by holding it underwater and drowning it. Eggs and chicks can fall victim to the kelp gull ("Larus dominicanus") and Pacific gull ("Larus pacificus"), particularly if parent birds have been disturbed. External parasites include the feather mite species "Morinyssus simplex"—collected from a museum skin of Australasian gannet—the bird louse species "Pectinopygus bassani", and the tick species "Ixodes eudyptidis", the widespread "Ixodes uriae" and "Carios capensis".