Declining representation of imperiled Atlantic Forest birds in community-science datasets

While monitoring is essential for effective conservation, obtaining occurrence data is often challenging, time consuming and expensive. The Brazilian Atlantic Forest has a high number of threatened and endemic species that need effective and urgent conservation actions informed by sound monitoring data. Community (or citizen) science surveys can provide cost-effective data for large areas over extended time and these geocoded and time-stamped observations can deliver information on species of conservation interest. We provide a spatio-temporal analysis of Least Concern, Near Threatened and globally threatened Atlantic Forest endemic bird species from iNaturalist, eBird and WikiAves and analyze species according to their global trends. Together, these three datasets contained 838,880 unique observations of 218 species in 2000–2022, including 95 threatened and Near Threatened species. While the absolute number of observations of threatened and Near Threatened species increased annually, their proportion decreased compared to the total number of observations. Similarly, the proportion of observations of declining species decreased. Through time, the number of non-specialist birdwatchers could have increased, with the higher survey effort resulting in a higher proportion of common (i.e., more easily observed) species. However, this pattern can also reflect real trends, as most threatened and Near Threatened species were declining, leading to decreased detectability and relatively fewer observations, even with the same effort and skills. Decreasing and threatened species need special attention and targeted monitoring. In spite of the biases inherent in non-structured datasets and the difficulties of surveying rare species, community science can provide an effective warning system, and can improve monitoring of species at high risk of extinction.