Habitat  fragmentation  is  a major  extinction  driver.  Despite  dramatically  increas-ing fragmentation across the globe, its specific impacts on population connectivityacross species with differing life histories remain difficult to characterize, let alonequantify. Here, we investigate patterns of population connectivity in six songbirdspecies from Singapore, a highly fragmented tropical rainforest island. Using massivepanels of genome-wide single nucleotide polymorphisms across dozens of samplesper species, we examined population genetic diversity, inbreeding, gene flow andconnectivity among species along a spectrum of ecological specificities. We found ahigher resilience to habitat fragmentation in edge-tolerant and forest-canopy speciesas compared to forest-dependent understorey insectivores. The latter exhibited lev-els of genetic diversity up to three times lower in Singapore than in populations fromcontiguous forest elsewhere. Using dense genomic and geographic sampling, weidentified individual barriers such as reservoirs that effectively minimize gene flowin sensitive understorey birds, revealing that terrestrial forest species may exhibitlevels of sensitivity to fragmentation far greater than previously expected. This studyprovides a blueprint for conservation genomics at small scales with a view to iden-tifying preferred locations for habitat corridors, flagging candidate populations forrestocking with translocated individuals and improving the design of future reserves.