Using community science to assess the breeding range and habitat quality used by a migratory passerine threatened at its range edge
These datasets and R code analyze threats to the Acadian Flycatcher (Empidonax virescens), a small Neotropical migratory passerine that is a habitat specialist and threatened in portions of its range, using community science data from the platforms eBird, iNaturalist, and Project NestWatch. This species is considered common throughout most of the eastern United States but is endangered in its northernmost breeding boundary of Ontario. This small range of endangerment has led to limited research on the drivers of the Acadian Flycatcher's small population size in Ontario and future population stability in the United States, motivating our research. Thus, we conducted a habitat and threat assessment for observations throughout the Acadian Flycatchers' breeding distribution from 2016-2021. This included spatial analysis of land cover and antagonistic and preferred species to Acadian Flycatcher nesting, environmental predictors of antagonistic and preferred species presence, range shift analysis of the northern and southern boundaries of the breeding range, and a concordance analysis of two community science platforms (eBird and iNaturalist). Our analysis shows that the Acadian Flycatcher is primarily observed in high-quality deciduous and wetland habitats even when surrounded by an agriculturally-dominated matrix and a potential avoidance of antagonistic species reflected by the low intersection of observations with Acadian Flycatcher observations. The analysis of environmental predictors of species of interest (antagonistic and preferred) indicates a positive relationship between blue jay presence and impervious cover and brown-headed cowbird presence and agricultural cover. These results suggest that the issues of nest predation and parasitism may become a greater threat to nesting success in the future with increasing habitat loss and fragmentation. We did not identify a range shift on either the northern or southern boundaries of the Acadian Flycatcher's breeding range. Our concordance analysis showed that the species of interest intersection results and habitat composition results were the same between different community science platforms, indicating the reliability of our results and the utility of community science data when answering research questions relating to spatial analysis. NOTE: Data for Project NestWatch is not publicly available.