Both morphological and behavioral traits predict interspecific social dominance in birds Interspecific dominance interactions have consequences for behavior, ecology, and the stability of species coexistence. Determinants of the outcomes of these interspecific interactions are therefore of great interest. However, few large-scale comparative works have demarcated the potential behavioral and morphological traits that explain dominance between species. To delineate which traits may influence species dominance, we rely on a newly established dominance ranking of bird species in North America. We pair these dominance rankings with phylogenetic analysis and incorporate social, morphological, and natural history variables to determine how morphological and social traits contribute. Like previous studies, we find that body mass is a positive predictor of dominance, but we also find that after controlling for body mass, bill length positively predicts a species’ rank in the hierarchy. In addition to morphological traits, we find that species that engage in proportionally more intraspecific fights tend to be less interspecifically dominant. Consequently, both morphological and social variables influence the interspecific dominance rank of a species. Such effects may have downstream consequences for the acquisition of foraging resources and the evolution of a species. Gavin M. Leighton, Dominique Lamour, Khalil Malcolm, and Eliot T. Miller. Both morphological and behavioral traits predict interspecific social dominance in birds. J Ornithol (28 September 2022). https://doi.org/10.1007/s10336-022-02022-y.