Bled, F., Nichols, J. D., & Altwegg, R. (2013). Dynamic occupancy models for analyzing species’ range dynamics across large geographic scales. Ecology and Evolution, 3(15), 4896-4909.
DOI: 10.1002/ece3.858
Through expanding citizen science efforts the large-scale biodiversity data required to predict species responses to global climate change are becoming increasingly available. But, drawing inferences from these large-scale data sets can be difficult as the data can be heterogeneous simply due to difficulties in collecting data in a standardized way. There is a need for a robust method to analyze the data that can account for variation in observation processes and spatial correlation. This paper seeks to develop a hierarchal occupancy model to analyze bird data collected across the southern portion of Africa. The use of this model is then illustrated by applying it to a study of the range dynamics of the hadeda ibis. To monitor bird species in southern Africa two atlas projects were established, in which citizens reported occurrence of species through species lists to a database. A hierarchical occupancy model was established to model occupancy at three levels (distribution at the scale of each atlas project, the yearly occupancy within each project, and the detection/non-detection on yearly use). The model was implemented on hadeda ibis, a large conspicuous bird that is unlikely to be mistaken for another species. The ibis had high occupancy probabilities across the ranges of both projects, with occupancy increasing from project one to project two. Based on geographic location of these projects this result reflects a range expansion of the ibis. This occupancy model for biodiversity data is conceptually similar to GAM-based species distribution models. As efforts for collecting data over larger extents continue this occupancy model will be useful in analyzing the data and allowing the researcher to address larger scale questions. This paper developed an occupancy model that utilized a citizen science project and demonstrated how the model could be used to study the range dynamics of a specific species. The authors conclude that the model could be used to answer many different macroecological questions and that range dynamics is just one example of how this occupancy model can be implemented.