The island biogeography of the eBird citizen‐science programme

AbstractAimIsland biotas face an array of unique challenges under global change. Monitoring and research efforts, however, have been hindered by the large number of islands, their broad distribution and geographical isolation. Global citizen‐science initiatives have the potential to address these deficiencies. Here, we determine how the eBird citizen‐science programme is currently sampling island bird assemblages annually and how these patterns are developing over time.LocationGlobal.TaxaBirds.MethodsWe compiled occurrence information of non‐marine bird species across the world's islands (n = 21,813) over an 18‐year period (2002–2019) from eBird. We estimated annual survey completeness and species richness across islands, which we examined in relation to six geographical and four climatic features.ResultseBird contained bird occurrence information for ca. 20% of the world's islands (n = 4,205) with ca. 8% classified as well surveyed annually (n = 1,644). eBird participants tended to survey larger islands that were more distant from the mainland. These islands had lower proximity to other islands and contained a broader range of elevations. Temperature, precipitation and temperature seasonality were at intermediate levels. Precipitation seasonality was at low and intermediate levels. Islands located between 10 and 60° N latitude and 20 and 40° S latitude were overrepresented, and islands located in Southeast Asia were underrepresented. From 2002 to 2019, the number of islands surveyed annually increased by ca. 96.4 islands/year. During this period, island size decreased, distance from mainland did not change, proximity to other islands increased and elevation range decreased.Main conclusionsThe eBird programme tends to survey larger islands containing intermediate climates that are more isolated from the mainland and other islands. These findings provide a framework to support the informed application of the eBird database in avian island biogeography. Our findings emphasize citizen science as an empirical resource to support long‐term ecological research, conservation and monitoring efforts across remote regions of the globe.