The common tern (Sterna hirundo) is a colonially breeding and migratory seabird. The data we collect come from a long-term study population located in the Banter See at Wilhelmshaven on the German North Sea coast. In 1992, 101 adult birds were caught and marked with transponders, and since 1992 all locally hatched birds have similarly been marked with a transponder shortly prior to fledging. The colony site consists of 6 concrete islands, each of which measures 10 by 5 meter and is surrounded by a 60 cm wall. The walls support 44 platforms for terns to land on, and each platform is equipped with an antenna that reads transponder codes to record the presence of all transponder-marked individuals. During incubation, which is shared between partners, additional antennae are placed at each nest for 1–2 days to identify breeding individuals. Combined with 3-times-weekly checks of nests to record reproductive parameters and to mark offspring, these methods enable the systematic and remote documentation of individual presence and reproductive performance at the colony. Once birds have established themselves as Banter See breeders, their re-sighting probability is almost 100% and their local survival probability is 80-90%, such that we can collect data over long individual life cycles. Since 1992, the number of breeding pairs has ranged between 90 and 740, annual reproductive success between 0.15 and 2.00 fledglings per breeding pair (averaging 0.81).