River flow is a major driver of community dynamics in riverine-floodplain ecosystems. Flow-induced disturbance can have large impacts on taxonomic groups at higher trophic levels such as birds. However, our understanding of river flow-avian relationships is constrained by a failure to focus on multiple species’ responses to hydrological variables across large geographical areas. The aims of this thesis are to combine a national-scale dataset of river bird surveys with river flow archives to: (i) understand how hydrological disturbance affects the distribution of river birds, and (ii) evaluate the potential impacts of climate change-induced shifts in river flow on such species’ distributions. Species have complex, but biologically interpretable, associations with hydrological variables. Variation in river flow acts as an environmental filter that influences community assembly processes. Specialist river birds are most vulnerable to climate-induced shifts in river flow and their distributions may shift in response to future changes in river habitat suitability. The success of relating hydrological variables to the distributions of river birds demonstrates that variability in river flow has consequences for ecological structure at high trophic levels and that climate-induced shifts in river flow may represent a previously unidentified mechanism by which climate change mediates range shifts in birds.