SummaryA Crested TemSterna bergiicolony containing 13 000–15 000 nesting pairs was located on North Bountiful Island in the Wellesley Group, Gulf of Carpentaria. This is Australia's largest known colony and may be the largest documented colony in the world. Breeding birds are thought to aggregate in autumn from foraging areas throughout the vast eastern Gulf of Carpentaria. The outer Wellesley Islands also support major colonies of Brown BoobiesSula leucogaster, Least FrigatebirdsFregata arieland a newly discovered colony of approximately 1000 pairs of nesting Roseate TemsSterna dougallii.Seabird nesting follows the summer monsoonal flooding and is presumably a response to nutrient enrichment of the Gulf by river runoff.