Most studies of avian communal signaling – individuals calling in coordinated unison – have focused on songbirds. Yet duets occur in 40% of species in the family Rallidae (rails and allies), one of the highest known rates of any bird family. We used a comparative approach to study links between duetting and life history traits, mass, habitat type, and call measurements across 90 rallid species. We predicted that duetters show long-term pair bonds and year-round territoriality, inhabit dense vegetation and produce low-frequency calls that spread well over short distances, and have similarly sized males and females; unlike non-duetters, in which the calling sex (males) should be larger. Phylogenetic generalized linear mixed-effect models found that duetting is significantly associated with year-round territoriality and lack of migration, and forest-dwellers are more likely to duet than species in open or heterogeneous habitats. Contrary to predictions, phylogenetic MANOVAs found that duetters call at higher frequencies, and no significant correlation exists between duets and pair bond length or size dimorphism. Our results indicate that rallids fit some, but not all, expected patterns seen in duetting birds generally. Despite the prevalence of duets in rallids, no experiments have tested duet functions such as resource defense in these understudied birds, and our evolutionary study lays the groundwork for future research. The innateness of rallid calls, in contrast to the learned calls of most songbirds, suggests that the causation and survival value of duetting, and possibly its behavioral purposes, differ in rails from the traditional avian study system.