This paper presents a summary of the four preceding papers and integrates them with previously-published data to compare demographic parameters of Roseate Terns breeding in tropical and temperate regions. Tropical Roseate Terns appear to breed less frequently than temperate birds and raise far fewer chicks to fledging when they do breed. Nevertheless, the three estimates of adult survival rates of tropical populations that were presented in this symposium are lower than those for temperate populations (0.71-0.82 yr-1 vs 0.83-0.90 yr-1). Two estimates of juvenile survival (from fledging to age 1 or 2 years) of tropical birds are slightly higher than comparable estimates for a temperate population, but the differences are not sufficient to offset the lower productivity. Data on ages at first breeding are similar in the two regions. Given their irregular breeding and low productivity, the true survival rates of tropical Roseate Terns must be much higher than those estimated in this symposium. The adult survival rates of temperate Roseate Terns are unusually low compared to other seabirds with similar life-history characteristics. This is partially offset by consistently high productivity, but the reported demographic parameters cannot account for the observed long-term increases in numbers of two well-studied regional populations. Despite intensive study of Roseate Terns in several parts of their world range during the last 25 years, important features of the demography of both tropical and temperate populations remain poorly understood.
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Vol. 31 • No. 3