The past 2.6 million years, earth has undergone periodic cycles of cooling and warming. Known as the Quaternary glacial cycles, these periodic fluctuations in global climate have been responsible for biotic diversification across the globe. During the cooling phase of the glacial cycles, water is locked up as ice at the poles, leading to a drop in sea levels and the formation of land bridges across islands. These land bridges allow for gene flow between isolated island populations and can have a varied impact on demography and speciation patterns, depending on the species biology. In this talk, I will discuss the impacts of the Quaternary glacial cycles on gene flow and divergence of two understory babblers commonly found across the forests of Southeast Asia. We leverage the important museum collections of these babblers from remote islands in Southeast Asia to understand the genomic affinity of these isolated populations. Our analyses suggest that Quaternary land bridges and paleo-rivers shape the population structure of birds on the remote islands in Southeast Asia.