The construction of spatial distribution maps and regional occupancy indices from opportunistic records

A major advantage of opportunistic citizen-science data is the wide spatial and temporal coverage it provides, relative to long-standing monitoring data obtained from transect sampling, for example. Opportunistic schemes are used to form atlases for many taxa, but only broad trends between multi-year survey periods have typically been studied. Optimal methods for analysing opportunistic data are required, with the aim of greater understanding changes in species’ distributions. We apply occupancy models to opportunistic data in order to create spatial maps and regional indices.