Space-time species distribution modeling with opportunistic presence-only data: a case study of passerines in a protected area

Over the recent decades, Europe has experienced a significant decline in common bird species, particularly farmland species, due to anthropic pressures like agricultural intensification. Protected areas, such as the Écrins National Park (ENP) in France, can help mitigate these impacts. We evaluated whether an opportunistic presence-only dataset collected by trained ENP rangers contains biological signals strong enough to support robust statistical inference. Using a generalized additive Poisson model with spatial and spatio-temporal covariates, monthly latent spatio-temporal Gaussian random fields, and a non-spatial inter-annual effect, we estimated the relative abundance of 76 passerine species on a regular grid, with occurrences aggregated per spatio-temporal cell used as a proxy for sampling effort. The model showed good calibration for most species (