Abstract
Aim Biotic interactions form a pillar of niche concepts but are frequently overlooked as range‐limiting factors. At local scales, ‘non‐excavator’ bird species—those that nest in tree cavities but cannot create cavities themselves—experience competition with other non‐excavators but experience facilitation by excavators such as woodpeckers. Our objective was to evaluate whether competition and facilitation mediate the range limits of non‐excavator species. Location USA and Canada. Time Period Contemporary. Group Cavity‐nesting birds (55 non‐excavators, 20 excavators). Methods Using eBird abundance maps, we modelled abundance of non‐excavator species within their non‐coastal range limits as a function of either (1) summed abundances of non‐excavator heterospecifics, (2) summed abundances of excavator heterospecifics, or (3) abundances of House Sparrows or European Starlings, two invasive ‘supercompetitors’. We also evaluated ‘edge–core’ models that included data for range limits and cores. Results At a cross‐species level, the effects of heterospecific non‐excavator and excavator abundance were not significant for ‘edge only’ models. At a species level, only 3 species (5% of the total) showed strong (≥ 95% confidence) competitive effects of non‐excavators and strong facilitative effects of excavators. However, invasive ‘supercompetitors’ were associated with low range‐limit abundance of non‐excavators; for example, House Sparrows showed significant negative effects on range‐limit abundance for nine out of the 17 (53%) non‐excavator species of similar size. ‘Edge–core’ models showed positive effects of heterospecific abundance (both non‐excavators and excavators) within range cores but not edges. Main Conclusions Our results are consistent with the ‘Eltonian Noise Hypothesis’, which suggests that biotic interactions ‘wash out’ at broadening spatial scales such that only abiotic variables correlate with species distributions at broad scales. Among‐species broad‐scale similarity and fine‐scale variation in habitat selection, as well as variation in phenology, may contribute to the limited evidence we found of competition or facilitation contributing to range limits.