As species interactions influence species distributions, attempts to work backwards from observed species distributions to infer the effect of a potential interaction have been enticing. The “natural removal experiment,” an approach that tests for patterns consistent with competition by comparing a species’ habitat relationships in sympatry and allopatry with a potential competitor, has held promise, but has often been limited by the scales of data required. The recent expansion of community science-based datasets invites renewed opportunity for investigation using this approach. We revitalize the natural removal experiment by applying it to ask whether the distribution of the Chestnut-backed Chickadee (Poecile rufescens; CBCH) is consistent with competition with the Black-capped Chickadee (Poecile atricapillus; BCCH) in urban areas. Using data from the community science project eBird, we compared relationships of CBCH relative abundance to urban- and forest-related variables in individual urban-centres and across regions of allopatry and sympatry with the BCCH. As predicted under competition, we found that in allopatry, the CBCH adopted habitat relationships similar to the less forested, more urban habitats of the BCCH at both the urban-centre and regional scale. By applying predictive modeling to “imagine” either the absence or ubiquity of BCCH across the studied range of CBCH, we found that sympatry with the BCCH suppressed CBCH abundance in urban areas, and that in their absence CBCH abundance increased, consistent with competitive release. These lines of evidence suggest that the observed distribution of CBCH is consistent with that expected under competition with the BCCH in urban areas. Expanding beyond this case study, we discuss important considerations in the application of this approach, which presents a significant opportunity for researchers to harness community science to conduct more powerful investigations of species interactions extending to broad spatial scales.

Tropical birds are purported to be longer lived than their temperate counterparts, but it has not been shown whether avian survival rates covary with latitude worldwide. Here, we perform a global-scale meta-analysis of 1,007 estimates from 249 studies of avian survival and demonstrate that a latitudinal survival gradient exists in the northern hemisphere, is dampened or absent for southern hemisphere species, and that differences between passerines and nonpasserines largely drive these trends. We also show that while extrinsic factors related to climate were poor predictors of survival compared to latitude alone, the relationship between survival and latitude is strongly mediated by intrinsic traits ― larger species with smaller clutch size had the highest survival. Taken together, our results suggest that interactions between intrinsic traits and lineage-specific effects surpass latitude and its underlying climatic factors in explaining global patterns of avian survival.