Knowledge of bat migration routes and phenology is still incomplete, especially for small-bodied species. Here we report on autumn migration over a mountain barrier (1200 – 1400 m a.s.l.) and analyse differences between short- and long-distance migrants based on acoustic monitoring of the number and direction of bat flights. The number of flights over the mountain passes peaked in September and then slowly declined. This pattern occurred for both long-distance and short-distance migrants, but long-distance migrants had a longer migration season. All bats migrated preferentially during milder weather (relatively dry, high temperature and low wind). As the migration season progressed, the proportion of southerly flights increased, and this tendency was stronger for long-distance migrants than for short-distance migrants. It appears that a proportion of the movements of short-distance migrants were associated with individuals commuting across the ridge to swarming and wintering sites on either side of the ridge. We conclude that long-distance migrants differ from other species only quantitatively: they have a longer migratory season and their migratory direction to the south is more defined. We hypothesise that the migration strategy of long-distance migrants depends on maximising the use of good weather windows rather than on persistent migration regardless of conditions.