Demographic responses to population recovery illustrated by 30 years of monitoring a once critically endangered parrot

1. Understanding how demographic rates change during population recovery is critical for evaluating conservation success and determining when populations become self-sustaining. However, documenting such transitions requires long-term monitoring across substantial changes in population size— conditions that are rarely met.

2. We leverage a 29-year capture-mark-recapture dataset from the echo parakeet population (Alexandrinus eques), a vulnerable endemic parrot of Mauritius island that recovered from fewer than 20 individuals to over 500 during the study period. Using multistate capture-mark-recapture models, we analysed encounter histories of 2734 known-aged wild individuals to estimate age and state-specific survival probabilities while accounting for temporal variation, transitions between breeding states and controlling for unequal recapture probabilities.

3. Demographic rates changed substantially during population recovery. Recruitment into the breeding population declined across all age classes as the population approached carrying capacity. Survival showed contrasting patterns: juveniles (<2 years old) exhibited a declining temporal trend (from 0.68 in 1994 to 0.57 in 2020), whereas adult survival remained stable across years, with breeding adults showing consistently higher rates (0.96–0.97) than non-breeding individuals (0.76–0.90).

4. Synthesis and applications. These findings highlight the dynamic nature of demographic processes throughout population recovery and emphasise the value of continued monitoring beyond apparent recovery to detect density-dependent shifts in demographic rates of wildlife populations.