Data from: Modeling effects of nonbreeders on population growth estimates

Adult individuals that do not breed in a given year occur in a wide range
of natural populations. However, such nonbreeders are often ignored in
theoretical and empirical population studies, limiting our knowledge of
how nonbreeders affect realized and estimated population dynamics and
potentially impeding projection of deterministic and stochastic population
growth rates. We present and analyse a general modelling framework for
systems where breeders and nonbreeders differ in key demographic rates,
incorporating different forms of nonbreeding, different life histories and
frequency-dependent effects of nonbreeders on demographic rates of
breeders. Comparisons of estimates of deterministic population growth
rate, λ, and demographic variance, math formula, from models with and
without distinct nonbreeder classes show that models that do not
explicitly incorporate nonbreeders give upwardly biased estimates of math
formula, particularly when the equilibrium ratio of nonbreeders to
breeders, math formula, is high. Estimates of λ from empirical
observations of breeders only are substantially inflated when individuals
frequently re-enter the breeding population after periods of nonbreeding.
Sensitivity analyses of diverse parameterizations of our model framework,
with and without negative frequency-dependent effects of nonbreeders on
breeder demographic rates, show how changes in demographic rates of
breeders vs. nonbreeders differentially affect λ. In particular, λ is most
sensitive to nonbreeder parameters in long-lived species, when math
formula, and when individuals are unlikely to breed at several consecutive
time steps. Our results demonstrate that failing to account for
nonbreeders in population studies can obscure low population growth rates
that should cause management concern. Quantifying the size and demography
of the nonbreeding section of populations and modelling appropriate
demographic structuring is therefore essential to evaluate
nonbreeders' influence on deterministic and stochastic population
dynamics.