Abstract In 1999, we compared demographic and biological parameters in Common Terns (Sterna hirundo) among three colonies located 10-26 km apart in Buzzards Bay, Massachusetts, USA. The three colony sites differed primarily in size, number of pairs, and length of occupancy by terns: Penikese Island (8 ha, 132 pairs, 3 yr), Ram Island (1.1 ha, 1,900 pairs, 8 yr), Bird Island (0.6 ha, 1,800 pairs, >65 yr). This study compared parental ages and origins, nesting phenology, clutch-size, chick growth rates, productivity, chick diets, feeding rates and foraging trip times among the three colonies. Common Terns breeding at the new colony on Penikese Island were significantly younger (mean age 6.8 yr) and laid later (mean laying date 25 May), had higher productivity (2.2 fledged chicks/pair) and higher chick growth rates than those at the old colony on Bird Island (means 11.7 yr, 20 May, 0.8 chicks/pair, respectively). Feeding rates were highest and foraging trip times for all types of prey were shortest at Penike...