A correlation between length of telomere restriction fragments (TRFs) and age has recently been demonstrated in several bird species. Comparisons of different-aged individuals within a population have shown that TRFs typically shorten with age and that this shortening continues throughout the life span of the species. In addition, it has been shown that telomere rate-of-change (TROC) correlates tightly with life span across several bird species. Previous studies of long-lived birds, however, have shown exceptions to these trends, demonstrating no declines in TRF length in adults in some cases and increases in TRF length with age in other cases. Here, we report known ages of individuals from a colony of Great Frigatebirds (Fregata minor) based on recaptures of leg-banded birds, including two individuals that were at least 44 years of age, the oldest Great Frigatebirds ever reported. Using a previously developed molecular technique, we report a predictable, nonlinear decline of TRF length with age in this population. Telomere restriction fragments decline more rapidly early in life but continue to shorten throughout the life span examined. The rate of decline in TRF for this species does not fit the tight correlation previously reported between TROC and life span in other species. Finally, we tested the ability to estimate age and age structure of breeding females on the basis of the calibration of TRF length and individuals of known age. Because of the slow telomere-attrition rate and the variability observed in TRF lengths at given ages, estimations of age of individuals and of estimated age structure of breeding birds in this population are not particularly reliable.