Data from: Accommodating temporary emigration in spatial distance sampling models

1.Model-based distance sampling is commonly used to understand spatial
variation in the density of wildlife species. The standard approach
assumes that individuals are distributed uniformly and models spatial
variation in density using plot-level effects. Thinned point process (TPP)
models for surveys of unmarked populations (spatial distance sampling)
better leverage the spatial information underlying individual encounters,
and in the presence of within-plot variation in density, may explain a
larger proportion of the spatial variation in density. However, existing
spatial distance sampling approaches are conditioned on the assumption
that all individuals are present and available for sampling. Temporary
emigration of individuals can therefore result in biased estimates of
abundance. 2.We extended spatial distance sampling models to accommodate
temporary emigration (TPP model). Using simulations of a thinned
inhomogeneous point process, we assessed the performance of the TPP model
relative to the temporary emigration distance sampling (TEDS) model, which
implies a uniform distribution of individuals. In addition, we compared
inferences between TPP and TEDS models using data for two passerine
species in Alaska. 3.Parameter estimates from the TPP model exhibited
improved coverage probability and precision relative to the TEDS model
including a 26% reduction in the coefficient of variation (CV) of the
population size estimate. 4.In the applied example, the TEDS model
indicated weak relationships between abundance and habitat covariates,
whereas the TPP model indicated strong relationships for those same
effects, suggesting that spatial distance sampling models can provide
considerably stronger inference in the presence of within-plot variation
in density. In addition, the CV of the population size estimates for the
two passerine species were 32% and 4% smaller under the TPP model.
5.Synthesis and applications. We expect our extension accommodating
temporary emigration will be a critical specification for spatial distance
sampling models, particularly for studies assessing changes in the
distribution and abundance of highly mobile species including passerines.