Demography of cape petrels in response to environmental changes
Résumé
Predicting the responses of populations in changing environments is an important
task for ecologists. Understanding the population dynamics of highlatitude
breeding species is critical given the particularly rapid environmental
changes that occur in these regions. Using long-term mark–resighting data
acquired over 53-years in Pointe Géologie, Terre Adélie, Antarctica, we estimated
age-specific demographic parameters and evaluated the effect of the
environment on survival of a poorly known species, the cape petrel Daption
capense. We then modeled the dynamics of this population using a life-history
model and performed prospective and retrospective analyses to estimate the
sensitivity of the population growth rate to demographic parameters, and to
quantify their relative contribution. Survival of cape petrel increased with age,
being 0.610 (±0.193) for juveniles, 0.739 (±0.158) for individuals from 2 to
4, and 0.920 (±0.031) for older individuals. Minimum age at first reproduction
was 3 years old, the age at which all birds were recruited was 14 years, and
mean age at first reproduction was 9.05 (±2.06) years. Adult survival increased
over time and was positively correlated with the southern annular mode
(SAM). The stochastic population growth rate was estimated at 1.019, and
adult survival over age 5 made the largest contribution to variance of the population
growth rate. Sensitivity analyses revealed that population regulation was
mainly driven by the SAM. Our results suggest that despite the decrease in
breeding success, the population of cape petrels at Pointe Géologie increased
due to the increase in immature and adult survival.