Protected area edges host more warm-dwelling bird communities than the rest of the landscape

Protected areas can mitigate climate-driven changes in species' abundances and community compositions. However, protected areas vary in size and habitat composition as do areas outside them. Our knowledge of how ecological communities are changing in a landscape under climate change and at the interface between protected and unprotected land is scarce. Here, we evaluated if the temperature niche composition of bird communities changed with the distance to the protected area edge, and whether this change was mediated by habitat type and heterogeneity. We used long-term monitoring data on breeding birds from Canada during 1997–2019. We analysed the variation in average temperature niche of bird communities' using the community temperature index (CTI) that allows quantifying the relative dominance of warm- or cold-dwelling species, and the impact of environmental change on communities' thermal signature. We found a lower CTI value indicating dominance of cold-dwelling species in the core of protected areas and far outside them, while edges are characterised by warmer-dwelling communities. Over time, we observed a similar increase in CTI inside and outside protected areas. CTI change over time depended on the habitat type, with fastest shifts in broadleaf forests. Our results suggest that the management of the entire landscape, habitat type and edge distance, may mediate climate change responses of wildlife communities. Minimising the edge effect of protected areas under climate change will be key, especially for preserving cold-adapted wildlife communities at high latitudes.