Annual survival rates of breeding adult roseate terns

Analyses of the capture-recapture data on 910 individual Roseate Terns (Sterna dougallii) trapped from 1978-1987 as breeding adults on nests on Falkner Island, Connecticut, estimate the average annual minimum adult survival rate to be 0.74-0.75. There was weak evidence of year-to-year variation in annual survival rates during the study period. The Jolly-Seber models used to estimate survival rates also generated estimates of population size and capture probabilities. To determine the relative importance of adult mortality and permanent emigration in contributing to the estimated annual loss of one-fourth of the breeding population will require further study of intercolony movement between all the major colony sites. Assuming that the loss of birds from the Falkner Island colony site is due mostly to mortality rather than permanent emigration, and that the survival rate of this breeding population is typical of the entire North Atlantic breeding population, then the survival rate of this endangered species is low in comparison to the survival rates of several other marine bird species in the orders Procellariiformes, Pelecaniformes, and Charadriiformes.