Dispersal and spatial scale affect synchrony in spatial population dynamics

A large body of theoretical studies has shown that synchrony among populati ons is critical for the long-term persistence of species in fragmented habi tats. Although the effects of dispersal and environmental factors on synchr ony have been investigated theoretically, empirical studies of these relati onships have been lacking. We explored the interplay between environmental and demographic factors (fecundity, survival, dispersal) on population sync hrony for 53 species of birds. We show that the interspecific differences i n mean synchrony were determined by global environmental factors whose acti on was Probably mediated by the abundance of each species. After removing t he effect of these global factors on synchrony, I-he residual synchrony was strongly correlated with dispersal distance. The relationship between disp ersal and synchrony was stronger for the species nesting in wet habitats th an for those nesting in dry habitats. Our results indicate that different f actors synchronize bird populations at different spatial scales, thus highl ighting the role of scale in understanding spatial population dynamics and extinction risks.