Density dependence maintains long-term stability despite increased isolation and inbreeding in the Florida Scrub-Jay

Isolation caused by anthropogenic habitat fragmentation can destabilize
populations. Populations relying on the inflow of immigrants can face
reduced fitness due to inbreeding depression as fewer new individuals
arrive. Empirical studies of the demographic consequences of isolation are
critical to understanding how populations persist through changing
conditions. We used a 34-year demographic and environmental dataset from a
population of cooperatively-breeding Florida Scrub-Jays (Aphelocoma
coerulescens) to create mechanistic models linking environmental and
demographic factors to population growth rates. We found that the
population has not declined despite both declining immigration and
increasing inbreeding, owing to a coinciding response in breeder survival.
We find evidence of density-dependent immigration, breeder survival, and
fecundity, indicating that interactions between vital rates and local
density play a role in buffering the population against change. Our study
elucidates the impacts of isolation on demography and how long-term
stability is maintained via demographic responses.