Bayesian skyline plots representing historical demographic trends of Aegithalos bonvaloti and A. fuliginosus . The x-axis is in unit of million years ago. The y-axis shows the scaled effective population size. The median estimate is enclosed within the 95% HPD limits. Black and grey represent A. bonvaloti and A. fuliginosus, respectively. Dotted lines show the Last Glacial Maximum (LGM).