Microclimate mediates the strength and direction of avian biotic interactions

Theory predicts that the strength and direction of species interactions can shift from being competitive in benign environments toward being facilitative in stressful environments. However, the environmental context dependency of species interactions has rarely been tested in animal communities. We capitalized on a 15‐year, landscape‐scale dataset, collected annually in a relatively stable old‐growth forest environment, to test the long‐held hypothesis that the strength and direction of species interactions might be mediated by climatic conditions. It is generally accepted that competitive and facilitative interactions drive the distributions of many species, but are rarely included in climate envelope models, and may partly explain poor predictive performance of species distribution models in the face of climate change. Using multi‐species dynamic occupancy models applied to long‐term data, we tested whether annual settlement by bird species could affect either the persistence or settlement by other phylogenetically related species, and whether these interactions are mediated by microclimate. We found that species interactions were influenced by microclimate for a high proportion of species pairs (80%). Related species pairs more often showed settlement dynamics that were indicative of attraction rather than repulsion (55 versus 30%, respectively). In some cases, competitive interactions in colder microclimates flipped to become facilitative in warmer ones (15%) and vice versa (5%). Furthermore, species pairs that were closely related were more likely to exhibit competitive relationships along at least part of the microclimatic gradient. Our results highlight the importance of using long‐term data to incorporate competitive and facilitative interactions into species distribution models, and support the notion that the strength and direction of species interactions can be dependent on microclimatic conditions.