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During 1971-75 and 1991-95, surveys of Caspian tern (Sterna caspia) colonies throughout New Zealand were carried out. The breeding population in 1971-75 was 1266 pairs, in 16 colonies, predominately in the northern North Is. In 1991-95, there were 1190 breeding pairs found in 17 mainly northern colonies, suggesting the population had been relatively stable over the 20-year period. As census methodology may under-record the breeding of isolated pairs, we included an estimate of the number of isolated pairs to give a total national population of 1300-1400 breeding pairs. This is less than 3% of the global population. Colony size and location showed some change between survey periods; 6 colonies disappeared and 8 new colonies were formed. Addition surveys in 2011-2015 are recommended to compare recent population trends.