That species and communities respond to biotic and abiotic environmental conditions over both short and long time scales and small and large spatial scales is, I woulda ssert, a fundamental tenet of ecology. Describing the nature of the associations of bird distribution and abundance with environmental variables has formed the basis for much of avian ecological research for well over a century, with an increasing focus not just on the correlations but also elucidating the mechanisms (physiological, demographic, etc.) that account for those relationships. Importantly, there is also recognition that the underlying biotic and abiotic conditions that determine a species’ distribution are dynamic in space and time, and that because of myriad anthropogenic factors, those conditions are changing at a pace likely unprecedented in the evolutionary history of most avian taxa. It is this recognition that motivates current research in establishing how bird species’ abundances and distributions have changed through time, which environmental variables or suites of variables are associated with those changes, what mechanisms appear to drive those changes, and how we can use this knowledge to predict how species might redistribute themselves in response to continuing environmental changes in the future. The 25 chapters in this edited volume fi comfortably within this framework.