The diet of the great crested tern consists mainly of pelagic fish from 10 - 15 centimetres in length, but it also opportunistically takes squid, crabs, insects, baby turtles, and other aquatic prey. It typically forages in groups, flying several metres above the ocean, every now and again plunging into the water or dipping its bill just under the surface to catch unsuspecting prey. Most foraging occurs within three kilometres of the colony (2) (5).
The great crested tern tends to breed in large, dense colonies or in small groups within larger mixed species colonies. Each breeding individual nests only once in any given year, with the nests being a shallow scrape in sand, gravel or coral, often packed tightly together (2) (5). The clutch size is usually a singe egg, or sometimes two, which are incubated for 25 to 30 days before hatching. The chick fledges after around 38 to 40 days but remains dependent on it its parents until it is at least 4 months of age (2).
Although most great crested terns appear to remain more or less within the vicinity of the breeding colonies throughout the year, the movement patterns of this species are poorly known (2) (5). Certainly, populations in Australia commonly disperse several hundred kilometres after breeding, while those in the Middle East typically over winter in Egypt and east Africa (2).