Figure 1.
Age-dependent reproductive success of blue-footed booby males from two cohorts. Reproductive success (fledglings produced per pair) was estimated as the standardized residuals from annual reproductive success of the colony. Showing longitudinal data on 13 males from cohort 1988 and 63 males from cohort 1989, which were ringed as chicks and survived 13 years. Individual reproductive performance varied with age (F1,179=21.69, p<0.0001) and age2 (F1,174=18.57, p<0.0001) and this effect was more pronounced in males hatched in 1988, although the interaction was no significant (cohort×age2, F1,174=2.67, p=0.10; cohort×age, F1,179=2.13, p=0.14; cohort, F1,195=0.49, p=0.48; male identity, p<0.01; study area, p>0.5).