Combining transient dynamics and logistic‐asymptotic growth to study the recovery of two seabird populations after rat eradication

Understanding demographic processes is crucial in ecology and conservation biology to assess how populations respond to environmental pressures. Although demographic parameters often react to disturbances, populations may remain in unstable age structures (transient dynamics) following such events. To explore the influence of transient dynamics in masked booby and red‐footed booby populations on Tromelin Island 15 years after rat eradication, we compared observed, transient, and asymptotic growth using count and capture–recapture (CR) data. CR data were used to estimate survival probability from Cormack–Jolly–Seber models and other vital rates such as breeding frequency and age at first breeding. We coupled asymptotic growth with a density‐dependent model for breeding site availability to project long‐term population growth. Both populations exhibited high adult survival (0.91–0.96) and breeding success (0.46–0.54). The masked booby juvenile survival was also high (0.86). Populations are expected to grow until breeding sites are saturated, in about a century. Comparison of asymptotic and transient growth suggests that population growth is linked to an intrinsic process and that both populations have undergone disruption in their age structure likely due to past predation by rats. Although the observed population growth appears to align more closely with transient growth, we could not entirely exclude the possibility that differences between asymptotic and observed growth rates may be due to data scarcity or age‐related variation in demographic parameters. Nevertheless, the study of transient dynamics allowed a better understanding of the differences observed between field counts and estimated asymptotic growth rates based on matrix population models.