The value of community science data to analyze long-term avian trends in understudied regions: The state of birds in Türkiye

Recent studies have revealed concerning declines in bird populations in Europe and other parts of the world. In understudied but biodiverse regions, especially those that are located along key migratory flyways, there is an unmet need to evaluate the status of resident and migratory birdlife for avian conservation ecology. This is especially urgent at a time when recent regional studies have highlighted the scale of the decline of the European and Palearctic avifauna. Rapidly growing community science datasets may help bridge the gaps in our understanding of long-term regional avifaunal trends. In this study, we used eBird data submitted by observers in Türkiye to undertake the first long-term assessment of the state of the country's birds from 2001 to 2022. We evaluated population trends based on presence-absence data of species to determine if any birds have significantly increased or decreased in the country so far this century. We provide a list of trends for 418 bird species that had large enough sample sizes of eBird observations from Türkiye, and highlight which species have significantly declined or increased. We found that 63 species have significantly declined in detection while 120 have significantly increased during the study period. Our findings provide a baseline for the future monitoring of Türkiye's birds and help contextualize population changes of birds in Türkiye against those occurring at the continental (Palearctic) scale. Additionally, we include movement classifications for all of the bird species in this study. We also provide a framework to effectively use eBird data to assess long-term avifaunal changes at the country-level in other understudied regions. Finally, we highlight ways in which eBirders in Türkiye and elsewhere can strengthen the quality and value of community ornithology data for population assessments and avian conservation ecology.