The rate at which climate is changing in northern latitudes presents a significant threat to bird populations that rely on boreal forests. Alterations in the distributions of trees and other plants as a result of warming will alter the habitat suitability of vast regions of boreal and hemiboreal forests. Climate change associated habitat alterations along with range expansions of bird species are likely to have substantial consequences on avian communities and biodiversity. Identifying factors that contribute to species coexistence and community assembly processes at local and regional scales will facilitate predictions about the impact of climate change on avian communities in these forest ecosystems. This paper provides a comprehensive review of historic and current theories of community ecology dynamics providing a theoretical synthesis that links the evolution of species traits at the individual level, the dynamics of species interactions, and the overall maintenance of biodiversity. Integration of these perspectives is necessary to provide the scientific means to face growing environmental challenges in boreal ecosystems.