Who and Where Are the Observers behind Biodiversity Citizen Science Data? Effect of Landscape Naturalness on the Spatial Distribution of French Birdwatching Records

The study of spatial bias in opportunistic data produced by citizen science programs is mainly approached either from a geographical angle (site proximity, accessibility, habitat quality) or from the angle of human behavior and volunteer engagement. In this study we linked both by analyzing the effect of observer profile on spatial distribution of recordings. We hypothesized that observer profile biases spatial distribution of records and that this bias can be explained by landscape naturalness. First, we established observer profiles from analysis of the temporal and spatial distributions of their records as well as record contents. Second, we mapped a naturalness gradient at regional and local scales. Using a dataset of more than 7 million bird records covering a time span of 15 years from the west of France, we defined four types of observer: garden-watchers, beginners, naturalists, and experts. We found that recording intensity could be related to naturalness at regional level; most visited areas were those where naturalness was on average lower i.e., close to population basins and highly accessible due to well-developed road infrastructure. At local level (neighborhood of recording sites), we found that experts and naturalists recorded in areas of higher naturalness index than those of garden-watchers and beginners. These results highlight how records contributed by different types of observer may lead to complementary coverage of different areas of the landscape. Future studies should therefore fully consider observer heterogeneity and how different observer profiles are influenced by local landscape naturalness.